Geological Journal of China Universities

Comparison of Protolith Assemblages of Metamorphic Rocks in the Dabie-Sulu Orogen and the Late Mesozoic Magmatic Rock Associations in the Coastal Region of Zhejiang and Fujian Provinces: Implications for theNeoproterozoic Tectonic Setting of Northeastern Yangtze Block

QIU Jian-sheng, HU Jian, LI Zhen, LIU Liang

2010, 16(4): 413-425.

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The Dabie-Sulu orogenic belt is tectonically situated in the northeastern margin of the Yangtze Block. This belt is mostly underlain by granitic gneisses (over 80%), and minor eclogites occur as pods or layers within them. The protoliths of the granitic gneisses and eclogites correspond to acidic and basic igneous rocks, respectively, and both of them are of Neoproterozoic ages. In this paper, the protolith assemblages and geochemical characteristics of these metamorphic rocks are systematically compared with those of the Late Mesozoic igneous rock associations in the coastal area of Zhejiang and Fujian Provinces.

Characteristics of Granitic Pegmatite with High-Purity Quartz in Spruce Pine Region, USA and Altay Region of Xinjiang, China

ZHANG Ye ， CHEN Pei-rong

2010, 16(4): 426-435.

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The alaskites/pegmatites from the Spruce Pine region of USA and the muscovite granites/pegmatites from the Altay region of Xinjiang, China, were comparatively studied. The pegmatites from both regions might be melt-vapor differentiation products of the peraluminous granitic magmas. The pegmatites from the Spruce Pine region with high-purity quartz were developed on the schist or gneiss background, whose major rock-forming minerals are rich in plagioclase, showing high Na/K ratios, high large-ion lithophile elements Sr and Ba contents, low high-field strength and rare earth elements contents, positive Eu anomalies，and low impurity elements contents in quartz. All these characteristics can be used as the discrimination criteria of high-purity quartz pegmatities. The Altay region of Xinjiang is abundant of pegmatites, and some samples studied showed the features which evidenced that the Altay pegmatite region has a perspective to find the gualified pegmatites with high-purity quartz.

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

2010, 16(4): 436-447.

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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

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

2010, 16(4): 448-456.

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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.

Extensional Fault-Bend Folding in Urxun Sag， Hailaer Basin

田继强,贾承造,段书府,李本亮,张荣虎,吴兴宁

2010, 16(4): 457-464.

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Urxun Sag in the middle Hailaer Basin is a typical Meso-Cenozoic terrestrial half-graben. In this paper, we firstly illustrate the structural features and evolution of the Hailaer Basin and then analyze the structural geometric characteristics of the seismic reflection profile across the rifting-period prototype basin of the southern Urxun sub-sag. The kink-bands in the hanging-wall are proved to be extensional fault-bend folds. Thus further modeling about the rifting-period prototype basin of the southern Urxun sub-sag can be done to playback the development process of its rifting-period structure with the extensional fault-bend folding theory. The research shows that the evolution of the rifting-period prototype basin of the southern Urxun sub-sag can be divided into four phases: the pre-faulting phase, the initial faulting phase, the intense faulting phase and the stable faulting phase. In fact, its different evolutional phases have different sedimentary thicknesses, different folding styles and different horizontal extensions. Its total extension turns out to be 3.42 km.

S-Wave Velocity Structures of the Crust and Uppermost Mantle, and Possion,s Ratios in Fujian Province

HUANG Hui, MI Ning*, XU Ming-jie, WANG Liang-shu, LI Hua, YU Da-yong

2010, 16(4): 465-474.

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In this paper, the receiver functions were obtained by analyzing the teleseismic P waveforms recorded by 12 broadband
temporary and 8 permanent stations in Fujian Province. By using the H- k stacking method, the average crustal thicknesses and
VP/VS ratios were estimated. The S-wave velocity structures of 0-80 km were gained through the linear inversion method. The
H-k stacking results show that the crustal thicknesses range from 28.4 to 32.8 km, decreasing from north to south and from inland
to offshore of the Fujian Province. Along the NW-SE direction, the Possion,s ratios can be separated into several zones, and the
Possion,s ratios in the coastal area are higher than in the inland area. The crust can be divided into three layers: the upper, the middle and the lower crust. Apparently, there are differences among the crustal structures. The low velocity layers of crust appear beneath many stations. The average S-wave velocity of the uppermost mantle is lower in the coastal area than that in the inland area. It may imply that a heat anomaly area occurs in the deep depth.

Tectonic Characteristics and Numerical Stress Field Simulation in Indosinian -Early Yanshanian Stage, Lower Yangtze Region

ZHUANG Jian-jian,YANG Feng-li, ZHAO Wen-fang

2010, 16(4): 475-482.

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Based on intensive research on the tectonic deformation characteristics in Indosinian-Early Yanshanian stage in
the Lower Yangtze region, this paper has simulated the tectonic strain rate and surface velocity through the “thin-shell” finite
element method. The modeling results indicate that the area around the junction between Qinlin-Dabie Orogen and Tanlu fault
suffered intensively compressional effect, the eastern South Yellow Sea was a strongly tensional area, while the Sulu orogen and
the Jiangshao fault were transpressional areas. The average strain rate of the Lower Yangtze region was about 5.0×10-15/s ~1.0
×10-14/s and the surface velocity was probably about 50 mm/a. Controlled by this kind of tectonic stress field, the Lower Yangtze
Block produced massive thrust nappe structures in a ramp style.

Tectonic Modeling Constraints on Lithospheric Characteristics of the Qiongdongnan Basin

WU Zhe , YANG Feng-li , WU Jian-xun

2010, 16(4): 483-491.

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The Qiongdongnan basin is an extensional basin formed in Late- Eocene. In this study, based on the flexure isostasy
principle and flexural cantilever model， we utilize 2D structurcal simulation software and calculate the effective elastic thickness
valuse (Te) and the extensional factors on 2D interpreted seismic profiles. The results show that the effective elastic thicknesses
vary in the range of 1-5 km, and their optimum value is 3 km. The extensional factors change between 1.3 and 1.5, about 1.5
for the post-rift period with forward modeling, and about 1.3 for the syn-rift period with inverse modeling. Finally, we discuss the
possible influential factors of the activity of the Red River fault in the Cenozoic and the South China Sea spreading.

Application of Fish Head Boudin Structure to Estimation of Competency of Adjacent Competent Layers

LIN Yan-hao, ZENG Zuo-xun

2010, 16(4): 492-497.

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The initial thicknesses of the original rock layers can be restored by various fish head boudins. Furthermore, we
can analyze the linear strain in Z and X axes of the strain ellipsoid of the original rocks by the layer thicknesses. In this article,
a method for estimating the viscosity ratios of adjacent competent layers was derived from the Strain Differential Refraction
Rheology Gauges. An application trial was made for two specimens of fish head boudins from the Tieshan area, Daye, Hubei
province. We obtained the viscosity ratios of two adjacent fish head boudin hornfels layers in marble matrix, which are 3.07 and
0.75, respectively.

Standard Well for Quaternary Research and Its Geological Interpretation in Qinhuai River Valley of Nanjing Area

XIONG Zhen,HOU Kang-ming,LI Qing-he,CHEN Jie

2010, 16(4): 498-509.

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Based on data of systematic age sampling, Quaternary sediment lithology and palynomorph assemblage analysis on the standard well (N06S6) for Quaternary research in Qinhuai River valley, a stratigraphic unit, Hanfu Formation since Late Pleistocene, was set up for Quaternary stratigraphy in the Qinhuai River valley. Five palynological assemblages were distinguished through an intensive study on pollens and spores from the well, and five stages in the evolution of vegetation and climate were
correspondingly reconstructed for the Late Quaternary in this area. The Quaternary paleoenvironment, paleoclimate and paleo-
landform was also recovered in the area, which indicates that the paleo-landform changed little and new tectonic movement during this time was weak in the study area.

Sandstone Detrital Composition and Provenance Analysis of the Permian Longtan Formation in Southeastern Anhui Province

DU Ye-long, LI Shuang-ying, KONG Wei-lun, WANG Song

2010, 16(4): 510-517.

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Detrital composition analysis of sandstone is mainly used to study the provenance of sediments and the tectonic
background evolution. The Longtan Formation is one of the major coal-bearing strata in South China. The characteristics of
sandstone detrital compositions of the Permian Longtan Formation in southeastern Anhui province show that the contents of
monocrystal quart is mostly 25%-40%, and the polycrystal quart 30%-65%. The quart in the fine-grained sandstone usually has
a corroded rim. The contents of feldspar show a great variation, mainly 5%-15% in the fine-grained sandstone and about 1% in
the medium- to coarse-grained sandstone; Lithic fragments are mainly 15%-25% in the fine-grained sandstone and 10%-20% in
the medium- to coarse-grained sandstone. The sandstone detrital compositions and provenance analysis indicate that the sandstone of the Longtan Formation was derived from the mixed sources of recycled orogen and subduction complex. Combining with the gravel characteristics and the regional tectonic setting, it can be inferred that the sources of the Longtan Formation in the study area were mostly derived from the collision zone between the Cathaysia Plate and the Yangtze plate, namely the Jiangnan orogen

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

2010, 16(4): 518-527.

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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.

Comparative Study of Geochemistry and Multivariate Data Analysis on Mixed Oils Accumulated in Ordovician Reservoir in Tahe Oilfield,Tarim Basin, NW China

TAO Guo-liang, QIN Jian-zhong,TENGER, ZHANG Mei-zhen,FU Xiao-dong,LOU Zhang-hua

2010, 16(4): 528-539.

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Quantificational discrimination of mixed oils is a hot concept and difficult point in petroleum geology and geochemistry research. This article shows a case study on Tahe oilfield, Tarim Basin, NW China. Comparative study of geochemistry and multivariate data analysis indicate that oils accumulated in Ordovician reservoir in Tahe oilfield are characterized by multi-stage hydrocarbon generation and mixed sources. The early-stage generated oils were biodegraded, thus the light hydrocarbons, alkanes, and regular steranes in present oils show features of later-stage generated oils. Quantitative data of tricyclic terpanes and hopanes with little influence of biodegradation were calculated through Alternating Least Squares algorithm. The results show that there were four end-member oils contributed to the mixed oils in this region. The end-members 1 and 2 indicate middle-upper Ordovician source rocks, and the end-members 3 and 4 indicate Cambrian source rocks. In the main area of Tahe oilfield, oilsgenerated from the Cambrian source rocks were more than those from the middle-upper Ordovician source rocks. But in the area around the main area, the middle-upper Ordovician source rocks were the major contributors. For the whole oilfield, the Cambrian source rocks were more important. This comparative research shows that the multivariate data analysis plays significant role in calculating proportions of mixed oils and identifying end-member oils. As an effective complement to traditional geochemistry study, multivariate data analysis is worthy to be popularized

Study on Reservoir Properties and Effect of Syndepositional Faults in the Shanghe Oilfield

LI Zun-zhi,YANG Zhi-Jun, WANG Si-wen,LI Ya-hui,JI You-liang,KANG Yun

2010, 16(4): 540-547.

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The Shanghe oilfield presents obviously stepping distribution of multi-ordered tectonic belts and multi-level slope belts from north to south, and clastic reservoir properties also have apparent regular pattern due to the structural features. By means of analyzing a large amount of data of reservoir properties, combined with structure research, it is considered that the reservoir properties of the same stratum in the Shanghe oilfield are getting gradually worse and worse from the Shang 1 area, through the Shang 2 area and the Shang 3 area up to the Shang 4 area in the direction from north to south. But within the same area, the reservoir properties are getting worse and worse with increasing burial depth. The boundary faults of the Shanghe oil field are primarily syndepositional faults, and the stratum depths of different blocks are thickened from north to south because of syndepositional growth faulting. Consequently, the variation of formation thicknesses controlled by synsedimentary fault activity is
the main influential factor of the reservior property differences for the same stratum in different areas of the Shanghe oilfield.

Provenance Analysis of Late Triassic Sediments in the Southern Ordos Basin

ZHU Zong-liang,LI Wen-hou,LI Ke-yong, CHEN Quan-hong, GUO Yan-qin

2010, 16(4): 547-555.

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The source rocks of the Late Triassic in the southern Ordos basin are mainly the Archaean highly metamorphosed schists and gneisses, and the Sinian to Paleozoic shallow marine clastic rocks and carbonates. Affected by different sources, the light and heavy mineral assemblages have different features in various areas of a sedimentation system. In the western Zhenyuan-Jingchuan area, quartz content of sandstone is relatively high, and the lithic debris is mainly the sedimentary rocks. To the
southeast, in the Tongchuan-Yaoxian area, feldspar and debris of igneous and metamorphic rocks are gradually increased. In the
southern region of the basin, the heavy mineral assemblage is of zircon + tourmaline + garnet type, controlled by sedimentation
channel net. There are mainly four distribution areas in heavy mineral association: the Huanxian-Zhenyuan-Jingchuan area in the west is characterized by garnet + zircon + tourmaline + leucoxene assemblage; the Changwu-Ningxian area in the south is characterized by zircon + tourmaline + leucoxene + garnet assemblage; the Huangling-Tongchuan area in the southeast is
characterized by garnet + zircon + leucoxene assemblage; and the Fuxian-Yan^,an area in the northeast is characterized by garnet
+ zircon + magnetite assemblage. They respectively correspond to their own ancestral rivers and sedimentary diffusion areas. In
the Fuxian-Yan^,an area, the REE patterns and geochemical characteristics of theYanchang Formation are nearly similar withthe Archean and Early Proterozoic metamorphic rocks to the northeast of the basin. In the Zhenyuan-Jingchuan area, the REE
patterns of the Yanchang Formation sandstones are nearly similar to the metamorphic rocks to the southwest of the basin. This is certainly genetically related. Consequently, it can be inferred that the structural evolution process of the southwestern and northeastern areas of the basin was different.

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