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Zircon Geochronology, Geochemistry and Petrogenesis of Granite from the Baimianshi Uranium Ore District in the Southern Jiangxi Province DONG Chen-Yang, ZHAO Kui-Dong, JIANG Shao-Yong, CHEN Wei-Feng, CHEN Pei-Rong, LING Hong-Fei, YANG Shui-Yuan J4    2010, 16 (2): 149-160.   Abstract （4276）      PDF （1545KB）（2868）       Knowledge map    Save The Baimianshi uranium ore district is an important volcanic-hosted uranium district in South China. The uranium ore bodies occur in basalts and sandstones in the Baimianshi volcanic-sedimentary basin. The basement of the basin is composed of the Baimianshi granite and the Xunwu metamorphic rocks. Previous studies indicated that the Baimianshi granite provided uranium for the mineralization. In this study, LA-ICP-MS U-Pb dating of zircons from the Baimianshi granite was made showing an emplacement age of (241±7) Ma. The Baimianshi granite is a medium-fine grained two-mica granite, characterized by high SiO2 contents (71.99%-73.82%), with high A/CNK ratios (1.15-1.28). It is enriched in Rb, Th, Ta and depleted in Sr, Ba, Ti and Eu, and characterized by variable REE contents with LREE enrichment and obvious Eu depletion. The Baimianshi granite has relatively high initial 87Sr/86Sr ratios (0.71162—0.71613) and low εNd(t) values (-13.9 — -12.2). Two-stage Nd isotopic model ages vary from 2.01 Ga to 2.15 Ga. Its magmatic zircons have low εHf(t) values (-15.1—-11.9), with Hf model ages of from 2.01 Ga to 2.21 Ga, which are similar to the Nd model ages. Petrography and geochemistry indicate that the Baimianshi granite belongs to strongly peraluminous S-type. Combined with geochronology and isotope compositions, it is thus considered that the Baimianshi granite might be derived from partial melting of the metamorphic rocks similar to the Taoxi Group. The geochemical characteristics of the Baimianshi granite are similar to those of other uranium-bearing granites in South China. Multi-stage metamorphism and re-melting resulted in uranium enrichment in granites. Later hydrothermal fluid activity associated with crustal extension might have leached U from the granite to form the Baimianshi U deposit. Reference | Related Articles | Metrics

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Study on Fluid Inclusions of the Dayinjian Mo Deposit in Xinxian County, Henan Province, China LI Hong-chao, XU Zhao-wen, LU Xian-cai, Wang Xu-dong, CHEN Wei, ZHAI Dong-xin J4    2010, 16 (2): 236-246.   Abstract （4193）      PDF （1400KB）（2518）       Knowledge map    Save The Dayinjian Mo deposit, as an important deposit in the Dabieshan Mo-polymetallic belt, has genetic links to monzogranite intrusion of Late Yanshanian, and has attracted extensive attention for great progress in recent exploration. Based on the petrography and microthermometry of fluid inclusions in the quartz veins formed in main mineralization stage, 4 types of primary fluid inclusions were identified, including: (1) aqueous-rich two-phase inclusions (L-type), (2) vapor-rich two-phase inclusions (V-type), (3) daughter mineral-bearing three-phase inclusion (S-type) and (4) CO2-bearing three-phase inclusions (C-type), The analysis results indicate that two main homogenization temperatures present at 280~320 ℃ and 200~220 ℃, respectively, while the salinities range in two intervals of 5.11%~9.98% (NaCleq) and 36.06%~42.78%(NaCleq), respectively. The densities of the trapped fluids vary from 0.91 g/cm3 to 1.10 g/cm3. Raman spectra of the inclusions indicate that water vapor is the dominant component with minor amount of CO2 (possibly a little N2 in some cases) in the gasous phase of the inclusions. The typical shift in oxygen isotope compositions suggests a mixing event between magmatic and meteoric water. In summary, the deposit is an intermediate-high temperature epithermal deposit, and the fluid mixing plays crucially significant roles in the mineralization. Reference | Related Articles | Metrics

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Zircon U-Pb Geochronology and Hf Isotopic Compositions of Hehuaping Granite Porphyry, Southern Hunan Province, and its Geological Significance ZHANG Rong-qing LU Jian-jun ZHU Jin-chu YAO Yuan J4    2010, 16 (4): 436-447.   Abstract （4119）      PDF （3756KB）（2651）       Knowledge map    Save The Hehuaping granite porphyry  is  located  to  the southeast of Wangxianling granite and  there are cassiterite-sulfide type, porphyry type and altered fragmented-rock type tin deposits related to granite porphyry. Zircon LA-MC-ICP-MS U-Pb age for granite porphyry is 154~156 Ma, with a weighted mean age of (154.7±0.5) Ma (MSWD=0.085, n=21), which suggests an early Yanshanian emplacement. The  in situ Hf  isotope analysis reveals 176Hf/177Hf ratios  from 0.282403  to 0.282597，and ε Hf ( t )  from -2.84 to -10.14 (peak value around -6.5)， and the two stage Hf model ages ( tDM2) ranging from 1.38 Ga to 1.84 Ga (peak value around 1.55 Ga)，which indicates that its parental magma was derived from the mixed sources of the lower crust and mantle. Based on several age data of inherited zircons from the tin-bearing granites in the neighbouring Nanling Range, it can be concluded that the granitoids related to tin deposits were mainly products of remelting of the Mesoproterozoic basement rocks Reference | Related Articles | Metrics

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Zircon SHRIMP U-Pb Dating of the Buried Granodiorite and Muscovite 40Ar/39Ar Dating of Mineralization and Geological Implications of Meiziwo Tungsten Deposit, Northern Guangdong Province, China ZHI Wei, SUN Xiao-ming, WU Yun-shan, SUN Yan, HUA Ren-min, YANG Yong-qiang, LI Wen-qian, LI She-hong J4    2010, 16 (2): 177-185.   Abstract （3882）      PDF （843KB）（2386）       Knowledge map    Save The Meiziwo tungsten deposit is located in eastern part of Yaoling-Meiziwo tungsten mineralization zone, northern Guangdong province. The 40Ar/39Ar age of muscovite formed in syn-mineralization period is (155.9±0.6) Ma, consistent with large scale tungsten and tin mineralization in the Mesozoic Yanshanian period in South China. This date represents the mineralization age of the Meiziwo tungsten deposit. The zircon SHRIMP U-Pb age of biotite granodiorite body, occurring at about 600 m level in the lower part of the mine, is (430.4±3.6) Ma. This age suggests that the granodiorite body formed in the Caledonian period has no genetic relation to the tungsten mineralization. Our new data disagree with the previously proposed model for the tungsten mineralization, i.e., two times of “five-story”mineralization overprinted each other in this deposit. The ages of the mineralization and granodiorite indicate that the formation of Meiziwo tungsten deposit may be related to an Yanshanian granite buried in a deeper level, and therefore, we expect that the ore bodies might have a larger extension in depth. Reference | Related Articles | Metrics

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Zircon U-Pb Dating and Hf Isotopic Compositions of Porphyrites from the Ningwu Basin and Their Geological Implications HU Jin-ping, JIANG Shao-yong J4    2010, 16 (3): 294-308.   Abstract （3876）      PDF （4325KB）（3164）       Knowledge map    Save Ningwu volcanic basin is one of the most important basins related to mineral deposits in middle-lower reaches of the Yangtze River belt. Four volcanic units occur in the basin, in an ascending order, the Longwangshan Formation, the Dawangshan Formation, the Gushan Foramtion and the Niangniangshan Formation, with some high-level sub-volcanic igneous rocks intruding them. Detailed zircon U-Pb dating and Hf  isotopic composition measurement were performed on  the host  rocks  (gabbro-diorite porphyrites) of  the Washan  iron deposit. The zircon U-Pb ages of  three samples are  (123±1) Ma,  (127±3) Ma and  (125±2) Ma, respectively.Together with previously published precise zircon U-Pb dating results for volcanic rocks (127 to 131Ma), these results have placed a better constraint on  the magmatic and mineralization activity duration of  the Ningwu volcanic basin. The zircons  from  the Ningwu porphyrites have εHf ( t ) values  from -6.3  to -8.6. Together with other available geochemical data,  the Hf  isotope data  indicate  that  the Ningwu porphyrites may have derived  from upwelling depleted asthenospheric mantle mixed with enriched mantle and crust, which was controlled by the extensive lithosphere extension at around 125 Ma. The lower εHf(t) values and slightly younger ages of  the gabbro-diorite porphyrites  than  their hosting volcanic  rocks may  indicate more crust material involvement in the porphyrite petrogenesis. Reference | Related Articles | Metrics

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Early Yanshanian NE Trending Sn/W-Bearing A-Type Granites in the Western-Middle Part of the Nanling Mts Region ZHU Jin-chu，CHEN Jun，WANG Ru-cheng，LU Jian-jun，XIE Lei J4    Abstract （3556）      PDF （754KB）（2633）       Knowledge map    Save In the western-middle part of the Nanling Mountains region there develops an Early Yanshanian (Jurassic) Sn/W bearing A-type granite belt. It is composed of Huashan, Guposhan, Jiuyishan and Qitianling granite batholiths and nearby granite stocks. This belt extends in a NE direction for more than 250 km. The total exposure area is over 3000 km2. These granitic bodies are usually multiple phased intrusions. The emplacement ages of their major phases are in the range of 165 ~153 Ma. The contemporaneous igneous rocks of intermediate composition (diorite, granodiorite, quartz monzonite), acidic extrusive rocks and mafic microgranular enclaves with mingling character are very common. The major phase granites are mostly porphyritic biotite granite, sometimes contain hornblende. They are acidic to ultra-acidic, weakly metaluminous to weakly peraluminous, rich in K2O and total alkalis, rich in LILE and HFSE such as Rb, Cs, U, Th, LREE, Y, Nb, Ta, Zr, Hf, Ga, as well as Sn, W etc. oreforming elements and F, Cl etc. volatile elements. On the discrimination diagrams of Whalen et al (1987) they are plotted in the A-type granite field. Their ISr values vary in the range of 0.7063～0.7182, εNd(t) values in the range of -1.7 ~ -8.0, t2DM values in the range of 1.1 ~ 1.6 Ga, which indicates that different proportions of mantle component were involved in their source materials, especially for the Huashan and Guposhan granites. These granite bodies are usually strongly fractionated. The emplacement ages of the later phase (or the additional phase) fine-grained granites are in the range of 146 ~151 Ma. Compared with the major phase, they are more ultra-acidic, per-aluminous, more enriched in Rb, Cs, U, Y, Sn, W etc. trace elements, but more depleted in LREE and Zr etc. HFSE. Petrochemically, they are close to the S-type granites. The Sn/W etc. mineralizations were found throughout the whole process of granite emplacement and evolution, beginning from the major intrusive phase, through the additional intrusive phase, up to the post-magmatic hydrothermal stage. The mineralization types are various, including skarn type, greisen type, quartz vein type, Li-F granite type, cassiterite-sulfide type, chloritized and structurally hydrothermal alteration type etc. The large even giant tonnages are not rare. It was generally considered, that the Sn/W mineralizations are usually related with the S-type granites. Establishment of Sn/W bearing A-type granite in Nanling Mts region provides important evidence for close relationship of Sn/W deposits with A-type granites. It is also significant in exploring the new Sn/W deposits in South China and worldwide. The Early Yanshanian post-orogenic extensional and thinning tectonic environment, upwelling of asthenospheric mantle and underplating of mantle mafic magma, crust-mantle interaction, high temperature melting of the lower crust, fractional crystallization and differentiation of granitic magmas, hydrothermal filling and alteration, these are key factors for rock-forming and ore-forming processes in the Nanling Mts. region. Related Articles | Metrics

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SHRIMP U-Pb Dating of Zircons from the Late Mesozoic Basalts in Eastern Zhejiang Province and Its Geological Significance CUI Yu-rong, XIE Zhi, CHEN Jiang-feng, YU Yun-wen, HU Li-hai J4    2010, 16 (2): 198-212.   Abstract （3525）      PDF （2058KB）（2729）       Knowledge map    Save The zircon U-Pb ages were dated by SHRIMP method for eight basaltic rocks occurred in the eastern area of Zhejiang Province，which were erupted during the Late Mesozoic and named as Lower and Upper rock series (LRS & URS). The weighted average 206Pb/238U age of the basalts from LRS is (120±1) Ma with Th/U ratios ranging from 0.65 to 2.44. The weighted average 206Pb/238U age of the basalts from URS is (103±2) Ma, with Th/U ratios ranging from 0.57 to 3.03. These data suggest that the zircons from both rock series are of magmatic origin and represent the formation times of the basalts of LRS and URS. Thus, it can be concluded that the formation time of the URS and LRS is significantly different, and the age data are consistent with the previous researches. It can also be found that most of the zircons from the LRS basalts have a relatively homogeneous ages with only a few ancient zircon relicts, which indicates that they have little crustal contamination during petrogenesis. Some zircon grains show core-rim structure with a core age of about 132 Ma and a rim age of about 120 Ma, which may indicate that the inherited grains were captured from the magma source, and imply that there exist magmatic rocks formed at about 130 Ma in the mantle or mantle-crustal boundary during the LRS magma activity. The magmatic zircons from URS basalts are very few, many detrital grains were dated with the ages covering almost all of the magmatic events in the South China block. It is suggested that the URS basaltic rocks were contaminated by clastic rocks which contained the detrital grains with different ages. Reference | Related Articles | Metrics

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Petrological and Geochemical Studies on the Intermediate-Basic Volcanic Rocks from the Middle-South Part of the Da Hinggan Mountains Lü Zhi-cheng1 2, DUAN Guo-zheng3, HAO Li-bo3, LI Dian-chao3, PAN Jun3, WU Feng-chang2 J4    Abstract （3515）      PDF （3096KB）（1156）       Knowledge map    Save The petrogenesis and tectonic background of Mesozoic volcanic rocks from the middle-south part of the Da Hinggan Mountains are closely related to the late stage evolution of the Southem Mongolia-Da Hinggan Mountains orogenic belt and to the genesis of copper-polymetallic deposits．Based on detailed fieldwork，petrological and geochemical studies on volcanic rocks have been carried on．The results show that the volcanic rocks，including basaltic trachyte，trachyandesite，trachyte and dacite，belong to cale-alkaline series．In major elements they are enriched in Si02，Na20 and K20，and depleted in Fe203，FeO，MgO and CaO；and in trace elements they are enriched in lithophile elements，and depleted in siderophile elements and Nb，Ta，Ti etc．In REE patterns they are generally LREE enriched，(87Sr／86Sr)t ratios are 0．7045～0．7077，mostly 0．7045～0．7055，and most of εNd(t)values are positive．The results suggest that partial melting of upper mantle in different degrees Was the major mechanism for generation of the volcanic rocks in the middle-south part of the Da Hingan Mountains。and the volcanic rocks were developed in the tensional tectonic setting．The Mesozoic volcanic activity was a response to the extension caused by upwelling of mantle plume of asthenosphere during the post-orogenic period of the Tianshan-Da Hingan Mountains belt，to the post-orogenic extension background of the Inner Mongolia-Jihei orogenic belt，and to compression background caused by closure of Mongolia-Okhotsk residual ocean in a scissors form． Related Articles | Metrics

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Relationship between Reservoir Properties and Chlorite Rims: A Case Studyfrom Yanchang Formation of South Ordos Basin, North China DING Xiao-qi, ZHANG Shao-nan, Ge Peng-li, WANG You-li J4    2010, 16 (2): 247-254.   Abstract （3474）      PDF （4390KB）（2280）       Knowledge map    Save The chlorite rims are frequently observed in clastic successions. Their content and occurrence may heavily influence the reservoir properties. By using thin section determination and SEM, BSE, EDX analyses, we studied occurrence, timing, mechanism of generation and contribution to porosity preservation for the samples from Yanchang Formation, South Ordos basin. The results show: (1) There exists a spatial coupling of chlorite development with the brackish water delta front facies depositional environment and the biotite-rich arkosic sandstone; (2) The formation timing of chlorite is not earlier than the initial compaction stage, but not later than the appearance of authigenic quartz; (3) Formation of chlorite rims could change the porosity micro-environment and prevent growth of authigenic quartz on the detrital quartz surface; (4) The intercrystalline pores in chlorite rims are of limited value for petroleum storage, but can somehow contribute to the reservoirs as pathways for acidic fluids circulation; (5) The constructive diagenetic role of chlorite rims is their weakening effect for the overburden stress and restricting effect for the autigenic quartz growth in certain degree. Reference | Related Articles | Metrics

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Study on Geochronological, Geochemical Features and Genesis of the Fufang Granitic Pluton in the Jiangxi Province, South China ZHANG Fang-Rong, SHU Liang-Shu, WANG De-Zi, SHEN Wei-Zhou, YU Jin-Hai, XIE Lei J4    2010, 16 (2): 161-176.   Abstract （3413）      PDF （6256KB）（2636）       Knowledge map    Save The Fufang granitoid pluton, outcroped in the middle part of Wuyi Mountain area, is a typical Early Paleozoic pluton in the eastern segment of South China. Based on large amount of geological data during regional geological survey, the authors carried out a systematic study on petrography, geochemistry and LA-ICM-MS zircon U-Pb dating for the Fufang pluton. This pluton is mainly composed of monzogranite, granodiorite and in less amount tonalite containing Al-rich mineral, such as garnet and sillimanite. The A/CNK values are 0.99~1.14, categorized as weakly peraluminous and strong peraluminous. In trace elements, the Fufang pluton is enriched in LILE Rb, Th, Cs and rare earth elements La, Ce, Nd, and depleted in Ba, Sr, Ta, P, Ti. Thus, the Fufang pluton is a low Ba-Sr granite on the whole. The Rb / Sr and Rb / Nb ratios are 0.56~1.19 (everaging 0.92) and 6.85 ~25.18 (everaging 15.43), respectively, higher than the average values of the upper crust in eastern China and the world. The Fufang pluton has a higher ∑REE with LREE enrichment. Their distribution patterns are clearly right-wing type with relatively clear Eu depletion (δEu = 0.44~0.61, averaging 0.53). The emplacement ages of the pluton obtained for zircons from 1 sample of granodiorite and 2 samples of monzogranite are ( 443.9 ± 3.5) Ma (MSWD = 1.09) , (443.1 ± 4.6) Ma (MSWD = 0.25) and (433.6±3.9) Ma （MSWD = 0.61）, respectively. The first two sets of data are consistent ages within error range which shows that they were resulted from the differentiation and evolution of a co-magmatic chamber. The later one is obviously later and belongs to the later stage of the Early Paleozoic. The research results show that the Fufang pluton is of S-type granite, derived from the continental crust by lower degree of partial melting and its source rocks were mainly composed of pelitic sandstone rocks. The formation was probably linked with the collision between the fragments of Cathaysia Old Land and Yangtze block or collision among the fragments of Cathaysia Old Land. The earlier granitoids of Fufang pluton were syn-orogenic, formed in a compression environment, while the later granitoids were origined in a post-orogenic extension environment. Reference | Related Articles | Metrics

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Igneous Petrotectonic Assemblages and Tectonic Settings: A Discussion DENG Jin-fu1, 2，XIAO Qing-hui 1, 2，SU Shang-guo1, 2，LIU Cui1，ZHAO Guo-chun1，WU Zong-xu1，LIU Yong1，2 J4    Abstract （3391）      PDF （962KB）（3100）       Knowledge map    Save This paper discusses igneous petrotectonic assemblages of various tectonic settings: 1. mid–ocean ridge spreading; 2. oceanic island; 3. island arc; 4. MORS–type and SSZ–type ophiolites; 5. active coutineutal marginal arc; 6.compositional polarity of subduction–related magmatic arcs; 7. continental collision; 8. continental rift; 9. stable craton or platform, etc. It is emphasized that the tholeiitic ( TH ), calc–alkaline ( CA ) and alkaline ( A ) series defined from various parameters by different authors have different scientific meanings. In this paper it is indicated that the same written terms of TH, CA and A but with various meanings could easily result in abuse of these terms, especially for the recognition of the tectonic settings. The difference between MORS – and SSZ –type ophiolites in terms of igneous petrotectonic assemblages is discussed. The lowest MgOwt% of the HMA is suggested ( Table 2 ), based on the data of petrological experiments. The terms of magnesian andesite–dacite and adakite are discussed, and in turn, the Kay's magnesian andesite–dacite of higher Sr/Y, lower FeO/MgO, and higher MgOwt% as well as higher Ni, Cr contents, are comprehensively used, which can be more satisfactory to define the slab–melt, rather than the single parameter of high Sr/Y. The various schemes of classification for the continental collision are indicated, and it is necessary to be careful for using these schemes. The post–orogenic and the continental rifting A type granites are suggested to be associated with or without the CA/r, respectively, and the meaning of A and CA, here, is determined by the Peacock's alkali–lime index. Related Articles | Metrics

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Origin and Tectonic Setting of the Early Mesozoic Granitoids in Qinling Orogenic Belt ZHANG Cheng-li1, WANG Tao2, WANG Xiao-xia3 J4    Abstract （3386）      PDF （1737KB）（2437）       Knowledge map    Save The Early Mesozoic granitoids in Qinling Mts are characterized by the metaluminous to peraluminous and moderateto high-K calc-alkaline rocks with enrichment in LILE and LREE and poorness in HFSE, as well as relative depletion in Nb and Ta, showing the geochemical features similar to those of post-collisional granitoids. Some of them are adakite-like and rapakivitextured granitoids. The adakite-like granitoids display high Sr and low Y contents, and rapakivi-textured granitoids show transitional geochemical characters from I- to A-type granites. The structure and geochemistry of these granitic intrusions, together with the bimodal features of the coeval lamprophyres and mafic dykes, suggest that the Early Mesozoic granitoids in Qinling Mts region were formed in a post-collisional setting. The early adakite-like granitoids were formed under the thickened crust during the early post-collision period. The large numbers of normal massive granitoids were produced under the crustal extension environment after delamination in Qinling Mts region, and the occurrence of rapakivi-textured and high differentiated granitoids indicates that Qinling region had evolved into the late stage of post-collisional environment. Related Articles | Metrics

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Petrogenesis of Indosinian High Ba-Sr Granites in Laoniushan Batholith, Shaanxi Province and Their Tectonic Implications Wang Yanfen， Shao Yi， Jiang Shaoyong， Zhang Zunzhong， Hu Jian， Xiao E， Dal Baozh J4    2012, 18 (1): 133-149.   Abstract （3367）      PDF （5683KB）（1995）       Knowledge map    Save        The Laoniushan complex granitic batholith occurs in Xiaoqinling orogen along the southern margin of the North China Craton. Zircon LA-ICP-MS U-Pb dating yields an age of 207.9±0.72 Ma for the Kangping pluton, which is the early-stage granites in Laoniushan batholith, indicating that they were generated from the Early Mesozoic magmatism. These granites are characterized by metaluminous, high silica and total alkalinity with high FeO*/(FeO*+MgO) ratios, LILEs (especially Sr and Ba) and LREEs, low HREEs and Y contents, and insignificant Eu anomalies, similar to the high Ba-Sr granites. In comparison to the typical slab-derived adakites, the Kangping granites have low compatible elements (such as Cr, Ni) and high K2O contents with high-K calc-alkaline features, and display insignificant fractionation of HREEs. During the diagenetic processes, the geochemical behaviors of these granites were mainly constrained by the fractional crystallization of amphibole (clinopyroxene), plagioclase (K-feldspar), and minor garnet. Element and isotope compositions suggest that the sources of the Kangping granites in Laoniushan complex batholith are the mixture of the ancient basement materials of Taihua Group and small amounts of enriched lithospheric mantle metasomatised by fluid/melt that was derived from pelagic sediments-bearing subducted slab. These granites were generated by partial melting of the lowest part of the crust due to the subducted slab break-off during the post-collision extensional stage of the continental collision and orogenic processes. Reference | Related Articles | Metrics

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Crustal Recycling and Genesis of Continental Alkaline Basalts: Case Study of the Cenozoic Alkaline Basalts From Shandong Province, Eastern China CHEN Lihui, ZENG Gang, HU Senlin, YU Xun, CHEN Xiayu J4    2012, 18 (1): 16-27.   Abstract （3299）      PDF （668KB）（1799）       Knowledge map    Save          Geochemically, continental alkaline basalts are similar to those oceanic island basalts, and are viewed as the representative of intraplate basalts in continents. Here we provide a case study of the Cenozoic basalts in Shandong Province,eastern China, to discuss the genesis of continental basalts. Spatially, the Cenozoic basalts can be divided into two kinds, the early three parallel volcanic belts and the late small and isolated volcanoes. The three belts including the Weifang belt and the Yishui belt in western Shandong, and the Penglai belt in eastern Shandong are less alkaline and are mainly composed of alkali olivine basalts and basanites, which show broad ranges of incompatible element ratios and isotopic values. The small and isolated volcanoes are more alkaline and are mainly composed of basanites and nephenilites, which are more homogenous in incompatible element ratios and isotopic values. Therefore, compared with oceanic island basalts, the parallel volcanic belts in Shandong can be regarded as shield-building stage basalts, while the small and isolated volcanoes correspond to the posterosional or rejuvenescent basalts. On the isotopic plots of Sr vs. Nd and Nd vs. Hf, both the Weifang belt and the Yishui belt show a two-endmember mixing array. However, there is minor difference of the enriched endmembers of these two arrays. The enriched endmembers are characterized by smaller Ce/Pb and elevated Ba/Th ratios, suggesting a signature of lower continental crust. However, such materials have much lower Th/La ratios and have excess radiogenic Hf contents relative to radiogenic Nd. Such geochemical signatures cannot be produced by assimilation of lower continental crust but by recycled lower continental crust (eclogite or garnet pyroxenite), which had undergone early melting in the mantle. The different arrays in isotopic plots of the two belts are alike those of the KEA chain and the LOA chain of Hawaii islands. Therefore, we propose that the parallel volcanic belts of Shandong be attributed to the plume activity and the recycled lower continental crust be important components of the plume. Geochemically,basanites and nepheninites of the late small and isolated volcanoes share many signatures with the carbonatite, e.g. the depletion of K, Pb, Zr, Hf, Ti in the primitive mantle-normalized grams. Therefore, we conclude that their mantle sources have been carbonated recently. The moderately depleted Sr, Nd, Hf isotopic compositions of these alkaline rocks indicate that the carbonated liquids might be derived from recycled young (Mesozoic?) oceanic crust. Reference | Related Articles | Metrics

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Chemical Weathering Characteristics and Controlling Factors of the Ili Loess, Xinjiang LI Chuan-xiang， SONG You-gui J4    2011, 17 (4): 611-619.   Abstract （3255）      PDF （853KB）（2166）       Knowledge map    Save The element distribution characteristics and chemical weathering intensity of the loess and paleosol at the Zhaosu section in the Ili Basin are preliminarily studied through element geochemical analysis. Through comparing with the type Luochuan loess-palesol section of the Quaternary aeolian deposit in the Loess Plateau, we draw the following conclusions. The contents of major elements in the loess and paleosol at the Zhaosu section in the Ili region show similar variations，which indicate that both of them experienced the similar degree of chemical weathering after deposition. Major elements have the same changing trend as that of the Loess Plateau, with enriched CaO and MgO and depleted Na2O and P2O5. CIA index, Na/K ratio and A-CN-K diagrams all indicate that the Ili loess and paleosol experienced weaker chemical weathering than that in the Loess Plateau. Furthermore, there is no obvious chemical weathering differentiation between loess and paleosol. The climate conditions such as hydro-thermal combination (precipitation, temperature and evaporation, etc.) may play an important role in chemical weathering of loess and paleosol in the Ili basin. Reference | Related Articles | Metrics

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Geochronology of Youshan and Pingtian Granites in Nanling Rangeand Its Geological Implication SUN Li-qiang, LING Hong-fei, SHEN Wei-zhou, HUANG Guo-long, TAN Zheng-zhong J4    2010, 16 (2): 186-197.   Abstract （3206）      PDF （1152KB）（2498）       Knowledge map    Save In previous studies, the Youshan granite and Pingtian granite located to the east of the Zhuguangshan composite granite body in Nanling Range were considered being formed in the Yanshanian period. In this study, we present LA-ICP-MS U-Pb zircon dating results which shows that the ages of the Youshan granite and the northwestern part of the Pingtian granite are (213.4±3.0) Ma and (238.8±2.2) Ma, respectively. These results indicate that the Youshan granite was formed by the Indosinian magmatism and the Pingtian granite is probably a composite granite batholith formed in the Indosinian and Yanshanian periods. In addition, it is revealed that both granites contain zircons having inherited cores with ages of Archean and 541 Ma~1 642 Ma, implying existence of Archean crust as well as Proterozoic crust containing rocks formed by several periods of magmatism in the source. Some of the zircons from the Youshan granite display dark rims (in CL images) with Yanshanian ages, which suggests that the granite was probably affected by hydrothermal fluids during the Yanshanian period. Narrow dark rims of zircons are also observed in the Pingtian granite, suggesting effect of hydrothermal fluids. Reference | Related Articles | Metrics

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Recognizing the TTG Rock Types: Discussion and Suggestion FENG Yan-Fang, DENG Jin-Fu, XIAO Qing-Hui, XING Guang-Fu, SU Shang-Guo, CUI Xian-Yue, GONG Fan-Ying J4    2011, 17 (3): 406-.   Abstract （3195）      PDF （667KB）（3043）       Knowledge map    Save         This paper briefly describes and compares  two  international classifications of  the  rock  types of TTG series：the Le Maitre’s QAP modal classification based on accurate mineral modes, and  the O’Connor's An-Ab-Or normative classification when the Q-norm is＞10%. Both modal and normative classifications are generally consistent with each other. The field 5 of the QAP is called tonalite as the root name. It includes trondhjemite and plagiogranite (adopted by part of the USSR geologists). The latter may be called as    light-coloured  (M≤10)  tonalite. However,  the  tonalite and  trondhjemite can be directly determined by using  the An-Ab-Or normative classification. Based on  the comparison between  the Le Maitre’s QAP modal classification and some Chinese modified QAP modal classifications, and paying attention  to some examples  for  recognizing  the TTG  rock  types using O’Connor’s An-Ab-Or normative classification by  the authors, several suggestions are proposed here as  follows:  (1) The Le Maitre’s QAP modal classification may be used for recognition of the TTG rock types, when the accurate mineral modes are available, and then the procedure is necessary to be determined whether these rock types are tonalite or trondhjemite using the M indexes. When the chemical data are available but the accurate modes are lacking, the O’Connor’s normative classification may be used. When both the accurate mineral modes and the chemical data are available, both classifications may be used for a better recognition of  the TTG  rock  types;  (2)  In  terms of widespread utilization of  the O’Connor’s classification  for  the Archean grey gneiss and granite-greenstone belt, and for some Phanerozoic magmatic arcs, a suggestion of using the O’Connor’s classification for  the orogenic belts  in China may be helpful  for  recognizing  the TTG  rock  types;  (3) A unified classification  is needed  for regional  igneous petrological  investigations, particularly  in China, because of  large available chemical data rather  than accurate mineral modes, then the O’Connor’s normative classification may be suggested; (4) The O’Connor’s classification  is actually a chemical classification, which is good for a comparison between the intrusive and volcanic rocks, as well as between the igneous rocks and  the experimental melts. Finally, a  two-step  recognition procedure  is suggested: Firstly, use  the TAS classification by Middlemost to discriminate the felsic rocks; and second, use the O’Connor’s An-Ab-Or normative classification for recognition of TTG rock types. Reference | Related Articles | Metrics

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An Overview of the Tectonic Evolution of North Qaidam UHPM Belt: from Oceanic Subduction to Continental Collision ZHANG Guibin, ZHANG Lifei, SONG Shuguang J4    2012, 18 (1): 28-40.   Abstract （3177）      PDF （1245KB）（2636）       Knowledge map    Save         The North Qaidam UHPM belt is a typical continental type subduction zone. Coesite inclusions were found from eclogite and country gneiss, and diamond inclusion from garnet peridotite. This paper is focused on the progress of petrology,thermobarometry, geochemistry and geochronology studies of Yuka, Luliangshan, Xitieshan and Dulan terranes in the North Qaidam UHPM belt. This belt is unique because subducted oceanic relics prior to the continental subduction and collision are well preserved, Combined with the published data, especially the two protolith sources for eclogites, we conclude that the North Qaidam UHPM belt experienced a tectonic evolution from an oceanic subduction to a continental collision. Reference | Related Articles | Metrics

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Spatial and Temporal Distribution and Characteristics of Granitoids in the Gangdese, Tibet and Implication for Crustal Growth and Evolution MO Xuan-xue1 2, DONG Guo-chen2, ZHAO Zhi-dan1 2, ZHOU Su1 2, WANG Liang-liang2, QIU Rui-zhao3, ZHANG Feng-qin2 J4    Abstract （3170）      PDF （3336KB）（1089）       Knowledge map    Save Granites are important components in the continents, and also closely related to mineral resources. Granites take c. 12% of the total area of Tibetan territory and about 80% （in area） of them are distributed in the Gangdese magmatic belt. Spatially, the Gangdese granitoid belt consists of three zones, i. e. , north, middle and south zones, as a result of the evolution of Neo-Tethyan Bangong Co-Nujiang ocean and Yarlung Zangbo Ocean. Temporally, the tectono-magmatie events in the Tibetan Plateau and the Gangdese can be divided into three stages： Pre-collisional （ 〉65 Ma）, syn-collisional （65 -45 Ma） and post-collisional （ 〈 45Ma）. Nd and Sr isotopes of granitoids in the Gangdese provide a hint for understanding the crust growth and evolution. Most of granites in southern Gangdese have positive values of εNd （t） （ ＋ 1. 64 - ＋ 5.21 ） and young Nd model ages tDM （ 〈500 Ma）, showing characteristics of the juvenile crust. It implies that the mantle material played a significant role in granite petrogenesis. Granites in middle and northern Gangdese, however, are characterized by negative εNd（t） （ -5.3 - - 17.3） and relatively older tDM, 1. 2 Ga and 2.0 - 2.5 Ga, implying a Neo- and Paleo-Proterozoic basement. Crustal material played a major role in granite petrogenesis for the latter case. Related Articles | Metrics

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Subdivision，Discrimination Criteria and Genesis for A Type Rock Suites LIU Chang-shi, CHEN Xiao-ming, CHEN Pei-rong, WANG Ru-cheng, HU Huan J4    Abstract （3121）      PDF （4912KB）（1280）       Knowledge map    Save This paper discusses the necessity for subdivision of A type suites into A1 and A2 subtypes and the judging criteria to distinguish them，based on new data obtained in study on A type suites in north Guangdong province and the data published in Chinese and overseas literature． The A type suites can be divided into two subtypes and three groups(A1 subtype：AS group；A2 subtype：ALAG group and AAG group)．The A1 subtype(AS group)is usually SiO2-undersaturated，metaluminous，and peralkaline-alkaline rocks，which include feldspathide syenites, a1kaline syenites and phonolites ．They are essentially characterized by existence of more or lass amount of feldspathide minerals such as Sodalite，nepheline，leucite etc．The A2 subtype is usually Si02-oversaturated，alkaline-subalkaline granitic rocks，which include the peraluminous，subalka1ine A type granites (ALAG group)，and the metaluminous，alkaline A type granites (AAG group)．Distinguishable from the ALAG group，the AAG group generally contains more or less amount of Ca-Na-or Na-pyroxenes and amphiboles ．Geochemically，the A1 subtype has relatively lower Si02(54.13％ ～61.29％)，higher ALK (12.65％ ～ 13.50％)，NK／A (0.85～1.03)，chlorine(50×10-6 ～9600×10-6)，R2(623，average，the same below)，Nb/Ta (15.69)，Zr／Hf(36.17)，Eu/Eu* (0.60)，LREE/HREE (15.18) and zircon．saturation temperature(833℃ )，and relatively lower R1(-263)，10^4 Ga/A1(2.4)，Y/Nb(0.34，similar to OIB source materials)and relatively lower fluorine(50×10-6～3523×10-6)．In contrast to A1 subtype，the AAG group of A2 subtype has relatively higher SiO2(71.93％-76.28％)，lower ALK(7.81％ ～9.80％)，chlorine(26×10-6～500×10I6)，R2 (318，in average，the same below)，Nb／Ta(13.09)，Eu／Eu* (0.29)and LREE/HREE (7.57)，and higher R1(2295)，10^4 Ga/A1 (3.93)，Y (1.64，similar to IAB source materials)，higher fluorine(6OO×10-6 ～1900×10-6)and zircon-saturation temperature(883℃ )．The ALAG group of A2 subtype is similar in geochemical properties to the AAG group，but is peraluminous．Using a series of diagrams of R1-R2，Y/Nb-Yb/Ta, Nb-Y - Ce and Nb/Ta-Nb，the A type suites can be readily distinguished into A1 and A2 subtype ．Based on the Nd，Sr isotopic data and using the mixing model of depleted mantle endmember and bulk crust endmember, it is calculated that the source materials for most A2 subtype granites of seven rock bodies are dominated by depleted mantle endmember component(68％ ～78％)．The mixing model of depleted mantle endmember and enriched mantle endmember shows that the source material components for A1 type rock suites are composed of EM4DM96-EM17DM83，and the enriched mantle endmember comprises only a minor proportion． Related Articles | Metrics

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Difference of Hydrocarbon Accumulation in the Foreland Thrust-fold Belt of the Southern Junggar Basin WEI Dong-Tao, ZHAO Ying-Cheng, A Bu-Li-Mi-Ti, CHEN Tao, YANG Hai-Bo, WU Liang-Yu, LI Shi-Hong J4    2010, 16 (3): 339-350.   Abstract （3104）      PDF （1424KB）（1726）       Knowledge map    Save The  tectonic evolution and hydrocarbon accumulation  in  the  foreland  fold-and-thrust belt of  the southern Junggar Basin  is complex.  In order  to  reveal  this complexity and  in  turn provide basic  information  for  regional petroleum exploration and  fundamental geological studies,  this paper analyzes petroleum accumulation  features. The study area  is characterized by structurally different segments along the east-west direction, and by structurally different belts along the north-south direction. The hydrocarbon accumulation  in  these different areas was discussed  from a variety of aspects,  including sources,  reservoirs,  traps, conduits, preservation, hydrocarbon accumulation and controlling factors. A strong difference in hydrocarbon formation is shown by reservoir age and source-reservoir-cap type in different geotectonic units. In the eastern segment (i.e., the Fukang fault belt), the Permian-sourced (including Jurassic-sourced) hydrocarbons were mainly accumulated in Jurassic reservoirs, and the hydrocarbon accumulation was predominantly controlled by  traps, preservation and reservoirs; In  the middle segment  (i.e.,  the  foreland  fold- and-thrust belt),  the Jurassic- and Permian-sourced  (including Cretaceous-sourced) hydrocarbons were mainly accumulated  in Paleogene and Cretaceous reservoirs, and the hydrocarbon accumulation was predominantly controlled by source rocks, oil-source faults and  reservoirs;  In  the western segment  (i.e.,  the Sikeshu sag area),  the Jurassic-sourced  (including Paleogene-sourced) hydrocarbons were mainly accumulated in Paleogene-Neogene and Cretaceous reservoirs, and the hydrocarbon accumulation was predominantly controlled by migration pathway and reservoirs. Reference | Related Articles | Metrics

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40Ar/ 39Ar Dating of the Guanshan High Sulphidation Type Cu-Pb-Au Depositin Jiangsu Province and Its Geological Significance LIANG Ye-Heng, SUN Xiao-Ming, ZHAI Wei, MA Chun, WU Zhi-Qiang, DING Cun-Gen, WANG Tang-Xi J4    2010, 16 (2): 143-148.   Abstract （3037）      PDF （1324KB）（2135）       Knowledge map    Save Guanshan Cu-Pb-Au deposit in Lishui basin of Jiangsu Province is a high sulphidation type epithermal deposit hosted in Late Mesozoic subvolcanic rocks. 40Ar/39Ar dating was performed on two sericite samples collected from sericitized subvolcanic wallrocks of Guanshan deposit. The results yield plateau ages of（120.8±1.0）Ma and（116.0±1.3）Ma，respectively, suggesting that the major mineralization of Guanshan belongs to the large-scale Mesozoic metallogenic event occurred in eastern China. During 125 Ma to 115 Ma, most part of eastern China was affected by extensional tectonic stress, resulting in large-scale magmatism and formed a series of fault-depressed basins, including the Lishui volcanic basin. In this basin, upwelling of deep-seated magma provided magmatic heat, triggered circulation of meteoric water, which mixed with magmatic fluid, and finally deposited the ore minerals in brittle fractures in the trachyte-porphyry wallrocks. Reference | Related Articles | Metrics

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Characteristics and Mechanics of Cenozoic Salt-Related Structures in Kuqa Foreland Basins: Insights from Physical Modeling and Discussion YIN Hong-Wei, WANG Zhe, WANG Xin, WU Zhen-Yun J4    2011, 17 (2): 308-317.   Abstract （3020）      PDF （3893KB）（1866）       Knowledge map    Save Salt  layer has a significant  influence on  the structural deformation and evolution of Kuqa  foreland basin. Structural styles are quite different in the strata beneath and above salt. Strata above salt are mainly deformed by broad folding, while strata beneath salt are mostly deformed by closely-spaced thrusts. Based on scaled physical experiments, we investigate the deformation pattern and mechanics of Kuqa salt-related structures. Modeling  results show  that Kuqa salt-related structures are primarily controlled by  regional compression and growth sedimentation. Salt structures near  the back end, such as Kelasu  fold belt, are controlled by regional compression, and salt structures near the front end, such as Qiulitake fold belt, have a significant influence from the heavy growth sedimentation in the nearby Baicheng syncline. Reference | Related Articles | Metrics

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SHRIMP Zircon U-Pb Age, Sr-Nd-Hf Isotopic Geochemistry and Petrogenesisof the Ehu Pluton in Northeastern Jiangxi Province ZHAO Peng, JIANG Yao-hui, LIAO Shi-yong, ZHOU Qing, JIN Guo-dong J4    2010, 16 (2): 218-225.   Abstract （2974）      PDF （1522KB）（2585）       Knowledge map    Save In this study, we present detailed SHRIMP zircon U-Pb chronology, major and trace elements, and Sr-Nd-Hf isotope data for the Ehu pluton in northeastern Jiangxi province, in an attempt to better constrain its petrogenesis. SHRIMP zircon U-Pb dating shows that the Ehu pluton was emplaced in the Early Cretaceous (121.7 Ma±2.9 Ma). Petrographic, elemental and Sr-Nd-Hf isotopic characteristics suggest that the Ehu granites are of S-type, generated by partial melting of Paleoproterozoic metasedimentary basement in the deep (>40 km) crust, with no fractional crystallization and mantle-derived magma mixing in their evolution. The upwelling of asthenosphere during the Early Cretaceous extensional tectonic regime in the region induced partial melting of the lower crust. Reference | Related Articles | Metrics

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Rb-Sr Isochron Age Dating of the Bangpu Large-Scale Mo-Cu Polymetallic Deposit, Tibet and Its Geological Significance ZHOUXiong,WENChunqi,ZHANGXuequan,CAOShengyuan,WUPengyu,ZHOUYu,FEIGuangchun J4    2010, 16 (4): 448-456.   Abstract （2919）      PDF （5705KB）（2144）       Knowledge map    Save          The Bangpu Mo-Cu polymetallic deposit is one of the typical large-scale porphyry deposits which lies in the eastern Gangdese metallogenic belt, Tibet. Its major  ore elements are molybdenum and copper, and its accompanying elements are lead and zinc. A monzonite granite-porphyry whole-rock Rb-Sr isochron age of (13.88±0.38) Ma with MSWD=1.7 was obtained which represents the crystallization age of the rock. Furthermore, a pyrite Rb-Sr isochron age of (11.0±1.5) Ma with MSWD=3.5 was obtained for Mo and Cu bearing ores which represents the age of later episode of Mo-Cu mineralization. Combining with the zirconSHRIMP U-Pb age （13.9±0.3） Ma and laser micro-probe 40Ar-39Ar age （13.9±0.9） Ma, it is shown that the rock-forming and ore-forming ages are mutually consistent. The molybdenum and copper mineralization lasted about 3 Myrs. The inital 87Sr/ 86Sr valu（0.706538~0.709190） and mantle composition percentage (Pm) (4.03%~ 51.65%) indicate that the primary magma might be derived from the mantle, and emplaced in the Gangdese extensional setting 14 Myrs ago. The mantle magma was interacted with crustal dioritic magma and contaminated by crustal materials during its ascending process. But generally speaking, the magma source was mainly mantle-derived.   Reference | Related Articles | Metrics

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Ore-Forming Mineralogy of W-Sn Granites in the Nanling Range:Concept and Case Study WANG Ru-cheng, ZHU Jin-chu, ZHANG Wen-lan, XIE Lei, YU A-peng, CHE Xu-dong J4    Abstract （2871）      PDF （1322KB）（2444）       Knowledge map    Save Tungsten-tin mineralizations in the Nanling Range are closely related to granitic magmatism. Ability of controlling the mineralization of granites (or ore-forming potential of granites) is simply revealed by (1) the sources of granites (or initianl W-Sn enrichment); (2) differentiation degree of granites; and (3) nature and activity of fluids during granite evolution. This work aims to preliminarily establish a research system of ore-forming mineralogy for tungsten-tin granites in the Nanling Range. Biotite,titanite, cassiterite, rutile, wolframite, scheelite and wolframoixiolite are essentially useful minerals in clarifying the ore-forming potential of granites. On the crystal-chemical basis, these minerals are separately discussed by their petrographic, internal textural and chemical features. Criteria of these minerals as indicators of pricinple granite-related processes are presented for initial W-Sn enrichment in granites, crystallization of granite and hydrothermal mobility of ore-forming metals in late stage of granite differentiation. Features of ore-forming minerals are compared among three types of Nanling W-Sn granites (metaluminous tin granites, peraluminous tin granites and peralumnious tungsten granites). Finally, a case study was made in the Qitianling granite complex, which is essentially composed of the Sn granites of Furong and Cailing, and the Xintianling W granite. The Sn granites are characterized by biotite and titanite as Sn-bearing minerals, which suffured hydrothermal alteration, leading to tin leaching and subsequent crystallization of cassiterite. However, the Xintianling granite contains magmatic scheelite and wolframite. The mineralogical system of W-Sn granites helps to deepen metallogenic study and exploration of W-Sn deposits, and will be improved and perfected during the further researches. Related Articles | Metrics

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A Review on Mixed Rocks of Terrigenous Clastics and Carbonates and Their Petroleum-Gas Geological Significance FENG Jin-Lai, HU Kai, CAO Jian, CHEN Yan, WANG Long-Gang, ZHANG Ying, WANG Mu, ZHAO Jian J4    2011, 17 (2): 297-307.   Abstract （2842）      PDF （3126KB）（3510）       Knowledge map    Save The present progress in research on mixed rock of terrigenous clastics and carbonates is reviewed in this paper, mainly including classification,  terminology, depositional environment, depositional modes and petroleum-gas geological significance. It  is proposed by a comprehensive analysis  that  the depositional  facies  favorable  for  the mixed deposition mainly cover coastal and shallow-lake  faicies,  following by shallow-sea shelf, shore-shallow  lacustrine and delta  facies. The study on  the depositional environment  implies  that  the  factors controlling  the development of coastal mixed-rocks  include  tidal effect,  relatively strong hydrodynamic condition and a shallow sea environment favorable for the living of lower organisms. In contrast, with respect to the shore-shallow  lacustrine  rocks,  the  factors are  frequent  lake-level and climate changes. Consequently, a deep discussion on  the depositional micro-facies and associated environmental  factors may be an effective way  to  improve and better  the classification and  terminology of  the mixed  rocks. Furthermore, a synthetic depositional model  for  the marine and  lacustrine environment  is suggested based on above-mentioned analyses, combined with case studies in Paleogene and Neogene middle-deep mixed rocks in the northwestern Qaidam Basin. In addition, the shore-shallow sea and lake areas of mixed deposition can form high-quality targets of reservoir and source rocks, based on factual research data on source and reservoir sequences associated with mixed rocks. Reference | Related Articles | Metrics

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Spatial-Temporal Distribution of Mesozoic Ore Deposits in South China and Their Metallogenic Settings MAO Jing-wen1, XIE Gui-qing1, GUO Chun-li1, YUAN Shun-da1, CHENG Yan-bo2, CHEN Yu-chuan1 J4    Abstract （2839）      PDF （5028KB）（4014）       Knowledge map    Save Based on extensive field investigation and precise geochronological data we proposed Mesozoic metallic mineralization in South China can be grouped into three pulses, i.e. Late Triassic (230~210 Ma), Mid-Late Jurassic (170~150 Ma), and Early-Middle Cretaceous (134~80Ma). The mineralization elements in these three pulses are different. The Triassic mineralization is Peraluminous granite-related W-Sn-Nb-Ta. The Mid-late Jurassic mineralization can be further divided into 170~160 Ma porphyry and skarn Cu and I-type granite-related Pb-Zn-Ag, and 160~150 Ma paraluminous granite-related polymetallic W-Sn. Although the Cretaceous mineralization lasted about 54 Ma, its peak ranged from 100 Ma to 90 Ma. The major types of the mineralization are epithermal Au-Ag-Cu and granite-related polymetallic tin (tungsten). The Triassic peraluminous granite-related W-Sn-Nb-Ta is a response to the post-collisional process of the South China plate with the North China plate. The Izanagi plate started to subduct beneath the Eurasian continent at ca. 180 Ma and then the porphyry copper deposits and vein type Pb-Zn-Ag deposits and their related I-type granitoids or aidakitic rocks formed when the subducted plate was teared up in several locations at 170~160 Ma.After then a big window occurred in the Nanling area, triggering the asthenospheric substance got into the upper crust so that developed large-scale high fractionation paraluminous granite and related polymetallic W-Sn mineralization. It was a relatively quiet period of 150~135 Ma in South China except for the Middle-Lower Yangtze River Valley area located in the northeastern margin of the South China plate. Because starting to change motion-direction to northeast the subucted plate was teared up along the Middle-Lower Yangtze River Valley which used to be a foreland basin of the Triassic Dabie-Sulu orogenic belt. A group of skarn-porphyry Cu-Mo-Au-Fe ore system and related I-type or aidakitic granites developed along the cross of the Middle-Lower Yangtze River Valley with the NE-trending faults at an age range of 145~135 Ma. From 135 Ma the subducted plate moved along several groups of regional-scale NE-striking fault zones comprising the Tan-Lu fault zone, which trigged the Eurasian continent to extensive extension. At the setting developed a lot of linear NE-trending Cretaceous faulting basins and metamorphic cores accompanied with volcanic rock eruption as well as epithermal Cu-Au-Ag ore system, granite-related polymetallic Sn (W) deposits and hydrothermal uranium deposits at age of 120~80 Ma with a peak of 100~90 Ma. Related Articles | Metrics

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Studies on Structures of Several Early Cretaceous Fossil Conifers in Fuxin, Liaoning Province and Its Geological Significance DU Bao-Xia, YAN De-Fei, SUN Bai-Nian, DENG SHeng-Hui, XIE San-Ping, WEN Wen-Wen J4    2010, 16 (3): 327-338.   Abstract （2814）      PDF （9040KB）（1818）       Knowledge map    Save The conifer fossils, Cephalotaxopsis haizhouensis Shang, Elatocladus cf. dunnii Miller et Lapasha and Elatides harrisii Chow, were collected from the Lower Cretaceous Fuxin Formation of the Fuxin Basin, Liaoning Province. Studies on the epidermal structures of  these  three species were carried out, and  the epidermal structure characteristics of Cephalotaxopsis haizhouensis and Elatocladus cf. dunnii account  for a warm and humid environmental condition. Based on  the more complete cuticle and clearer stomatal bands structures, the analysis and comparison of epidermal structures between extant and fossil plants show that Cephalotaxus sinensis and Cephalotaxus fortunei can be the nearest living equivalent species to Cephalotaxopsis haizhouensis and Elatocladus cf. dunnii. The Early Cretaceous CO2 concentration of the Fuxin Basin was quantitatively reconstructed based on the analysis of these two fossil species and their living equivalent species. Reference | Related Articles | Metrics

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Methods in studying petroleum accumulation systems in a superimposed basin: A case study of petroleum reserviors in the central Junggar basin JIN Zhi-Jun J4    2011, 17 (2): 161-169.   Abstract （2718）      PDF （1943KB）（1746）       Knowledge map    Save The basic method  in studying petroleum accumulation system  in superimposed basins was demonstrated by a case investigation  in petroleum  reserviors of  the central Junggar Basin. The method can be summarized  into  two points. The  first  is that  the study  is  focused on petroleum reserviors. The second  is  that both organic and  inorganic geochemical methods are used. The case study  in  the central Junggar Basin shows  that  the area has at  least  two petroleum accumulation systems according  to the organic (biomarker in particular) studies, i.e., the Permian system in the eastern area to the Penyijingxi sag, and the Permian and Jurassic system in the middle-eastern Mosuowan area. The study using inorganic geochemical method on reservoir diagenetic calcite shows  that  the area has  two additional petroleum accumulation systems,  i.e.,  the Permian and Jurassic system  in  the surrounding area of the Dongdaohaizi sag and the Permian system in the Shidong area. Moreover, the potential of retaining oil and gas  for each petroleum accumulation system was assessed  to provide  information  for  the exploration. Therefore,  it  is concluded that the research method of petroleum accumulation system can help to improve the guidance on petroleum exploration, and the organic and inorganic geochemical methods are complementary to each other. In particular, the new application of the inorganic geochemical method is a supplement to and improvement for the previously and commonly used organic geochemical method, and thus deserves to be studied further. Reference | Related Articles | Metrics

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Hydrous amorphous calcium carbonate: A biomimetic mineralization study GUAN Ye-bin， YAO Qi-zhi， ZHOU Gen-tao J4    2011, 17 (1): 46-52.   Abstract （2706）      PDF （1879KB）（2401）       Knowledge map    Save A common route  to  form biogenic minerals during biomineralization  is  that  the  initial deposit of  transient amorphous precursor phases and subsequent transformation into one of more stable crystalline phases. In terms of biogenic calcium carbonate minerals, amorphous precursor phase is generally considered to be formed under the joint regulation of biological macromolecules and  inorganic  ions.  In  this work, amorphous calcium carbonate  (ACC) was synthesized  in  the presence of citrate anions by a biomimetic mineralization process. Structure and morphology of the synthesized ACC and the subsequently products from the ACC transformed were characterized using a wide range of techniques, including field emission scanning electron microscopy (FESEM), X-ray diffraction (XRD), Fourier infrared spectroscopy (IR) and thermal gravity analysis-differential thermal analysis (TG-DTA). The results showed that the multi-carbonate anions could induce the formation of ACC which had a similar composition to biogenic hydrous ACC. Therefore, our results suggest that some biomineralization-associated acidic biomacromolecules canalso induce the formation of biogenic ACC and transiently stabilize it. Related Articles | Metrics

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Experimental Studies on Fluid Inclusions in Hydrothermal Anhydrite：Effects of the Formation of Gypsum WU Xue-mei J4    Abstract （2704）      PDF （2034KB）（2144）       Knowledge map    Save Hydrothermal anhydrite [CaSO4] is a good host for primary and secondary fluid inclusions. It is also potentially a problematic host for stretching of inclusions, partial dissolution and precipitation of anhydrite, and formation of gypsum from reaction of anhydrite with the trapped aqueous fluid. Microthermometric experiments on liquid/vapor inclusions in anhydrite from Juan de Fuca Ridge show that new daughter crystals, identified to be the low-temperature hydrate gypsum [CaSO4?2H2O], commonly develop during freezing experiments (~-50℃).This phenomenon has been recognized for over 20 years, but its occurrence and significance to the determination of inclusion salinities are not widely appreciated. There is growing evidence that hydration of the host anhydrite may significantly lower the ice melting temperature and increase the salinity of the residual inclusion fluid. The present study shows that the salinities of inclusions increase largely after gypsum formed in liquid/vapor inclusions (salinities increase 0.32 to 1.6% NaCl eq.). We propose that gypsum is the product of both anhydrite hydration and supersaturation with respect to gypsum, but mainly owing to the former. Heating inclusions to decompose gypsum results in the release of bound water, restoring the inclusions to their original salinities. So when gypsum formation occurs during freezing experiments, it needs to be dehydrated periodically through heating to about 130℃. These processes could have no impacts on the real homogenization temperatures of inclusions. Related Articles | Metrics

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Magmatism and Evolution of the Tibetan Plateau MO Xuan-Xue J4    2011, 17 (3): 351-.   Abstract （2682）      PDF （15256KB）（7302）       Knowledge map    Save The Tibetan Plateau  is one of  the regions  in China where  igneous rocks are very widely developed. Various  types of volcanic and plutonic rocks are distributed over 300,000 km2 in area and take 10% area of the entire Plateau. These igneous rocks and carried deep-seated nodules play  important  roles  in understanding geodynamic evolution of  the Tibetan Plateau, as either lithoprobes/windows or  tectonic  records, and are closely  related  to mineralization as well. This paper discusses some  important scientific  topics via studying  igneous  rocks.  (1) The  timing of  Indo-Asia collision: This  is a very  important scientific problem. There  is, however, a wide  range of discrepancy about  the  timing of  initiation of  the collision  (from earlier  than 70 Ma,  to even later than 34 Ma). According to multiple lines of evidences from the 1500 km-extending main collision zone in southern Tibet, we deduced a conclusion that Indo-Asia collision likely started from 65/70 Ma and completed in c. 40 Ma (syn-collisional stage), and then transformed into post-collisional stage after 40 Ma. (2) Underplating and magma mixing, an event of mantle-crust interaction during  syn-collisional  stage: There are abundant evidences  for underplating and magma mixing  in  southern Gangdese. An important process of continental growth and evolution took place in the Tibetan Plateau. (3) The origin of formation of extremely thick crust of  the Tibetan Plateau: A deduction of “Two  types of crust and  two  types of mechanism”  is suggested based on  the studies of collisional and post-collisional  igneous  rocks. There are  two  types of crust,  juvenile crust and  recycled crust,  in  the Plateau. Crustal  thickening of  the Plateau was caused by  two  types of mechanism,  i.e., both structural compression and  input of mantle materials via magmatism. (4) The composition, structure and evolution of the lithosphere of the Tibetan Plateau: There are three geochemical reservoirs in the lithospheric mantle, and three types of lithospheric structure underneath the Tibetan Plateau. Nodules and outcrops of mantle/lower crust-seated rocks are found in several locations of the Plateau. (5) Possible lateral flow of lower crust and upper mantle: Migration of collisional and post-collisional volcanism with time shows a highly distinctive pattern, which can be interpreted to reflect lateral flow of the lower crust and asthenospheric mantle induced by the approach and ensuing collision of relatively thick (India and Eurasia) continental plates. Reference | Related Articles | Metrics

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Review on Application of Geobarometry for Granitic Rocks LI Xiao-Wei, HUANG Xiong-Fei, HUANG Dan-Feng J4    2011, 17 (3): 415-.   Abstract （2676）      PDF （742KB）（2800）       Knowledge map    Save        This paper briefly and critically discusses several common geobarometers applied  to granitic systems, especially the specific  rock  types, and  their  limitation and error analysis. The Al-in-hornblende barometer can be applied  to calc-alkaline granites and  is  suitable  for  low-pressure mineralized granitic pluton. The Fe-rich orthopyroxene-fayalite-quartz assemblage barometer can be used  to calculate  the crystallization pressure condition of  rapakivi granites, and  the crystallization pressure of coexisting alkali  feldspar, plagioclase and quartz can be obtained via projecting onto  the Q-Ab-Or-H2O phase diagram  for granites. The hydrostatic pressure of  fluid  inclusion  in granites can be acquired by  thermodynamic state equations or    raman spectroscopy. Some  indicative minerals  like magmatic epidote  sometimes can constrain  the  lower pressure  limit. Moreover, the pseudosection calculated by THERMOCALC   eventually can define  the pressure scope  for a specific coexisting mineral assemblage and specific pressure and temperature. Reference | Related Articles | Metrics

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Detecting Crustal and Upper Mantle Structures of the Eastern Margin of the Ordos Using Receiver Functions HUANG Tao， MI Ning， WANG Liang-shu， XU Ming-jie， LI Hua， YU Da-yong J4    2011, 17 (4): 569-576.   Abstract （2647）      PDF （2465KB）（2041）       Knowledge map    Save        A data set of 1876 three-component, P wave seismograms from 22 stations deployed at Ordos and Taihang mountains was collected to investigate crust and upper mantle structure of that area. By using the array deconvolution method, the vertical, radial, and tangential receiver functions of all events are obtained. All radial receiver functions are then migrated to produce a seismic image. The image shows that from Ordos to Bohai Bay basin, the crust becomes thinner from about 52 km to 37 km, and the Moho generally dips to the west at a small angle. In central part of Ordos basin, the crust is thickest, reaching 52 km; at the eastern edge of Ordos, the thickness decreases to 43 km. From Taihang Mountain to Bohai Bay basin, the thickness of the crust changes from 45 km to 37 km. Under the Shanxi Graben, the Moho suddenly uplifts by approximately 8-10 km in comparison to that of both sides, and the rise of the Moho and the depression of the surface show a mirror-image relationship. Reference | Related Articles | Metrics

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W-Sn-Nb-Ta-Bearing Granites in the Nanling Range and Their Relationship to Metallogengesis CHEN Jun, LU Jian-Jun, CHEN Wei-Feng, WANG Ru-Cheng, MA Dong-Sheng,ZHU Jin-chu, ZHANG Wen-lan and JI Jun-Feng J4    Abstract （2599）      PDF （3275KB）（3047）       Knowledge map    Save The large-scale mineralizations of W, Sn, Nb and Ta related to granites took place in the Late Jurassic period in Nanling Range, South China. According to the petrological and geochemical features of ore-bearing granites and their relationship to mineralizations, they can be grouped into the following three major types: W-bearing granites, Sn-W-bearing granites and Ta-Nb-bearing granites. The W-bearing granites show low TiO2 and Ba+Sr contents and LREE/HREE ratios,intensive Eu depletion, high Rb and Y abundances and Rb/Sr ratios, and oversaturation in Al. They commonly underwent intensive differentiation and evolution. The Sn-W-bearing granites are characterized by enrichment of TiO2, total REE, HFSEs,Ba+Sr and Rb, higher CaO/(K2O+Na2O) and LREE/HREE ratios, metaluminous-weakly peraluminous feature and lower Rb/Sr ratios, and weaker differentiation and evolation. The Ta-Nb-bearing granites have very low TiO2, Ba+Sr, total REE and HFSEs contents and CaO/(K2O+Na2O) ratios, higher Al2O3/TiO2 and Rb/Sr ratios, higher Rb and Nb contents, and ACNK values. They are highly evolved. Good discrimination can be obtained between these three types of W-Sn-Nb-Ta-bearing granites on plots employing Nb-Y-Ce, (Ba+Sr)-Rb-(Zr+Nb+Ce+Y), LREE/HREE-Rb/Sr and LREE/HREE-(Zr+Nb+Ce+Y) diagrams. These three types of ore-bearing granites have obviously different evolutional trends. Metallogenesis is intimately related to the evolution of the ore-bearing granites. Mineralizations of Sn, W or W-Sn and Nb-Ta or Sn-W-Nb-Ta are closely related to biotite granites, twomica granites or muscovite granites and albite granites respectively. The important deposit types of W, Sn, Nb and Ta and their major features in the Nanling Range are summarized in the paper. The chloritized granite type tin deposit is proposed. This paper indicates that an attention to searching for both the chloritzed granite type tin deposits and greisen-quartz vein type W-Sn deposits in W-Sn-bearing granites in the Nanling Range should be especially paid. Related Articles | Metrics

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Discovery of Impact Ejecta from Taihu Lake Impact Crater WANG He-nian, XIE Zhi-dong*, QIAN Han-dong J4    Abstract （2599）      PDF （11020KB）（3063）       Knowledge map    Save The hypothesis of impact origin of the Taihu Lake was proposed about twenty years ago, but never confirmed.Recently some weird-shaped concretions were found embedded in the mud layer in the vicinity of the Taihu Lake, which might be impact ejecta from the Taihu impact crater. These new samples comprise two categories. One is rich in iron with fine siderite as concretion matrix, including abundant small spheroid concretions, stick-shaped concretions, and irregular shaped concretions.The other one is poor in iron with calcite as concretion matrix, including twisted-shaped concretions. The fragments embedded in matrix mainly consist of angular-sharp-edged quartz grains, and minor fragments of clay and plagioclase minerals. The sizes of the ejected materials range from centimeters of massive rocks to millimeters even to micrometers of the spheroids. Most hand samples show abundant semi-plastic features, such as twisted shape and molten crust, which might be caused by their flying in the air in the molten or semi-molten status. All these features suggest that these new samples once experienced a series of the impact cratering processes, such as the shock-induced fragmentation, shock-induced melting, ejection into the air, flying in the air, and falling in and around the impact crater. The components of the ejected materials are consistent with the target rocks in the Taihu Lake area. The confirmation of impact ejecta is another important discovery after the discovery of the shock-induced microfeatures in deformed quartz in the sandstone of islands in the Taihu Lake. The discovery of the ejection materials, combining with other features, confirmed the impact origin of the Taihu Lake. Related Articles | Metrics

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Geochemical Characteristics and Genesis of Crude Oils of Carboniferous and Triassic in Tahe Oil field of Tarim Basin ZHENG Chao-Yang, LIU Yi-Qun, DUAN Yi, XU Wen-Xiu, FAN Ting-Ting, ZHANG Xue-Jun J4    2011, 17 (2): 249-259.   Abstract （2580）      PDF （1506KB）（1835）       Knowledge map    Save Because Tahe oil field is the largest marine carbonate rock oil field of the Tarim Basin, its genesis is of great interest. By means of  to  the high-resolution GC-MS analysis of  the oil samples  from Carboniferous and Triassic Tahe oil  field,  this paper studies biomarkers and discuss  their genesis. The Pr/Ph, Pr/nC17 and Ph/nC18 data  indicated  that oil  formed  from  sapropel organic matters of reducing environment. Abundance of gammacerane C30+ hopane  indicates  that  the oils  formed  from saltwater environment. The abundance of C27  sterane,  tricyclic  terpane,  tetracyclic  terpane, and higher  tricyclic  terpane vs hopane parameters show that original source materials are homonemeaes. Rearranged sterane/sterane, Ts/(Ts+Tm), and C29ββ/(ββ+αα) are 0.24~0.40，0.28~0.50 and 0.56~0.63，respectively. All of  these show  that  the maturity of  the oil  is high. The occurrence of 25-norhopane  indicates  that  the oil experienced some degree of biodegradation. Comparison of oil and source rock suggests  that the oils of the main source rock came from the middle-upper Ordovician source rocks. Reference | Related Articles | Metrics

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Element Geochemistry of Lake Sediments from Sihu Lake in Guilin Karst  Wetland Region and Its Environmental Effect SHEN De-fu, LI Shi-jie, CAI De-suo, ZHANG Hong-liang,ZHAO Xiang-gui J4    2010, 16 (4): 518-527.   Abstract （2580）      PDF （993KB）（1858）       Knowledge map    Save          Sedimentation rates and element concentrations  of core sediments from Sihu Lake are investigated and characteristics of element geochemistry and environmental change around  this  lake are discussed. By using principal component analysis,  the geochemical composition factors affecting the sediments of the cores are mainly four: the erosion factor, the watershed runoff and diagenesis factor, the regional background effect factor and the human activity effect factor. The latter two factors usually account for smaller proportions. However,  in recent years  the human  factor has rapidly numerical  increase because of quick  increase of phosphorus contents  in  lake sediments. On  the other hand, variations  in chemical elements obviously have periodic  feature:  the fourth period (0-4 cm, corresponding to 1987-2007), is mainly affected by human activities closely related with regional economic development. The other earlier  three periods  (4-20 cm, corresponding  to 1894-1987; 20-53 cm, corresponding  to 1703-1894; 53-77 cm, corresponding to 1562-1703) were mainly controlled by climate change. Reference | Related Articles | Metrics

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Characteristics and Genesis of Mesozoic A-Type Granites and Associated Mineral Deposits in the Southern Hunan and Northern Guangxi Provinces along the Shi-Hang Belt, South China JIANG Shao-Yong, ZHAO Kui-Dong, JIANG Yao-Hui, DAI Bao-Zhang J4    Abstract （2550）      PDF （2672KB）（2122）       Knowledge map    Save The Shi-Hang belt is an important magmatic zone composed of granites with relative higher εNd(t) values and younger tDM model ages and trends NNE. The granites in Southern Hunan and Northern Guangxi include the Qianlishan, the Qitianling,the Xishan, the Jinjiling, the Huashan and the Guposhan granites. Recently a series of zircon SHRIMP U-Pb ages indicate that all these granites were emplaced in a narrow time interval of 151~163 Ma. However, ages of granites decrease from the southwest to the northeast. These granites have similar geochemical characters. All of them are enriched in alkalies and potassium, and have high contents of LILE and HFSE. In geochemical discriminating plots, these granites fall in A-type granite field. Thus, the Southern Hunan-Northern Guangxi granite belt belongs to an A-type granite belt. These granites are further classified to A2 type.These granites have relatively lower (87Sr/86Sr)i values, higher εNd(t) values and younger t DM model ages. From the southwest to the northeast, εNd(t) values gradually decrease. Abundant mafic microgranular enclaves were found in most granites. Petrogeology and geochemistry, especially Hf isotopes of zircon from the MMEs and host rocks indicated that these granites formed by crust-mantle magma mixing processes. The mantle-derived magma end-member came from depleted mantle, and might be directly related with the asthenospheric mantle. The A-type granite belt might form at back-arc or intra-arc extension environment triggered by subduction of palaeo-Pacific plate. The strong mantle-crust interaction caused by upwelling and underplating of the asthenospheric mantle across the trans-crustal faults is the major mechanism for generating the A-type granites in the belt. The extension and thinning of the continental crust began from the southwest to the northeast, and the intensity of extension decreased from the southwest to the northeast. The Shi-Hang South Belt is an important W-Sn mineralization belt. All these granites belong to Sn-rich granite. Mechanism of tin concentration in these granites is different with common tin granites, in which tin is concentrated by fractional crystallization. Tin mineralization models are abundant in the belt. Different with traditional tin mineralization model,tin mineralization in the Furong tin deposit was related with chloritization of granites by later meteoric water hydrothermal system.Studies on these granites and related tin mineralization may enrich mineralization theories of A-type granites. Related Articles | Metrics