Table of Content

20 June 2016, Volume 22 Issue 2

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Mineralization Age of the Maoping Pb-Zn Deposit in the
Northeastern Yunnan Province: Evidence from Rb-Sr
Isotopic Dating of Sphalerites

SHEN Zhanwu, JIN Canhai, DAI Yanpei, ZHANG Yu, ZHANG Hai

2016, 22(2):  213. 

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The Maoping Pb-Zn deposit is a typical ore deposit in the northeastern Yunnan province. However, there is no precise
geochronological data to date. This research performed Rb-Sr isotopic dating on four sphalerite separated from the Maoping deposit,
which yielded isochron age of 321.7 ± 5.8 Ma (MSWD=1.5), indicating that the mineralization age of the Maoping deposit was
Carboniferous. Moreover, the 87Sr/86Sr ratio of sphalerites is determined to be 0.712166 ± 0.000017. This result is lower than that of
continental crust (0.719) and higher than mantle (0.707), implying that the ore-forming metals were derived from continental crust with
a minor amount of mantle-derived materials. Combining with the previous studies, we propose that the Maoping deposit is an epigenetic
deposit similar to the typical MVT Pb-Zn deposits and its mineralization has no link with Permian Emeishan flood basalts. Moreover,
we also suggest that multi-stage Pb-Zn mineralization most likely occurred in the northeastern Yunnan province.

Ages of the Cu-Ag -Pb-Zn Polymetallic Deposits in Western Lanping Basin, Yunan Province

ZHANG Jinrang, WEN Hanjie, QIU Yuzhuo, ZOU Zhichao

2016, 22(2):  219. 

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The Lanping basin is a significant Pb-Zn-Cu-Ag mineralization belt of the Sanjiang Tethyan metallogenic province in
China. A series of sediments-hosted Himalayan Cu-Ag-Pb-Zn polymetallic deposits have been discovered in the western part of the
basin, which are controlled by a thrust-nappe system. In the thrust-nappe system, the Cu orebodies occur as vein-type deposits in the
western and relatively deep part of the mineralization system (the root zone), mainly including the Jinman Cu-Ag deposit, Liancheng
Cu-Mo deposit, and more than 30 small vein copper deposits, such as Kedengjian, Huangbai, and Enqi. The Pb-Zn-Ag(± Cu)

orebodies mainly occur in the eastern and relatively shallow part of the system (the front zone), including the Baiyangping
Pb-Zn-Ag-Cu ore belt, and some small Ag-bearing Pb-Zn deposits, such as Liziping and Wudichang. To define the metallogenic
history of the Cu-Ag-Pb-Zn polymetallic deposits in western Lanping basin, we dated nine calcite samples associated with copper
sulfide from the Jinman Cu deposit by the Sm-Nd isotopic analysis and five molybdenite samples from the Liancheng Cu-Mo deposit
by the Re-Os isotopic analysis. The nine calcite samples yielded an age of 58.2 ± 5.3 Ma (2σ, MSWD = 0.039). The five molybdenite
samples yielded an isochron age of 47.8±1.8 Ma (2σ, MSWD=7.2). The Sm-Nd isotopic age of calcites from the Jinman deposit (58 ±5 Ma)
and the molybdenite Re-Os age for the Liancheng deposit (48 ± 2 Ma), together with previously published chronological data,
demonstrate that (1) the main Cu-Ag (Mo) mineralization in the root zone took place at ca. 56~48 Ma, corresponding to the
main-collisional stage of the Indo-Asian collision orogeny; Possibly, there was a remobilization or a new phase of Cu mineralization in
the duration from 35 to 47 Ma; (2) The main Pb-Zn-Ag (± Cu) mineralization in the front zone took place at ca. 31~29 Ma,
corresponding to the late-collisional stage of the Indo-Asian collision orogeny.

Lithogeochemistry and LA-ICP-MSZircon U-Pb Age and Its
Tectonic Significance of Sujishan A-type Granite Pluton，
Eastern Bogda Mountains

LEI Wanshan, GUO Junfeng, Ma Jihai, XIAO Liang, LI Xiangchuan，LIU Junfeng，LI Yon

2016, 22(2):  231. 

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The Sujishan granite, formed at Balikun, Xinjiang province, is a ferro-edenite alkali-feldspar granite, locating tectonically at
the eastern segement of the Bogda orogenic belt. Containing high contents of SiO2, K2O+Na2O, NK/A and low content of Al2O3, it
invariably exhibits light rare earth elements (LREE) enrichment with weak negative Eu anomalies and enrichment of LILE and HFSE
with the depletion of Cs, Sr, P, Ti. The element combinations of high HFSE (Zr+Nb+Ce+Y) range from 451×10-6 to 674×10-6 and
zircon-saturation temperature lies within 841℃ to 883℃. These characteristics show that it belongs to A-type granite, and specifically

most of the samples fall into the range of A2-type granite according to the discrimination diagrams. The amphibole as rock-forming
mineral belongs to calcic amphibole group, ferro-edenite hronblende subgroup, which is characterized by Al2O3 2.9%~4.5% and Si/(Si+
Ti+A1) 0.88~0.93, implying a crustal source. The zircon LA-ICP-MS U-Pb dating analysis suggests the emplacement age of Sujishan
granite is ca. 301.5±2.4Ma, which belongs to the Gzhelian stage of the late Carboniferous. Sujishan A-type granite with crustal-derived
amphiboles differs from A1-type granitoid representing a stretching mechanics related with mantle plume or rifting. Additionally, the
emplacement time at middle and late of rifting differs from A2-type granitoid formed at a post-orogenic tectonic stage. In combination
with granites emplaced at adjacent region, the Sujishan A-type granite marked a limited stretching mechanics related with rifting,
which may be the product of oblique subduction of the paleo-Asian Ocean plate along the Kalameili subduction belt .

Geochronology and Geochemistry Characteristics of the Granites from
the Huashigou Area, South Qilian and Their Tectonic Significance

HU Wanlong, JIA Zhilei, WANG Jinrong*, HOU Kexuan, WANG Shuhua

2016, 22(2):  242. 

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The monzonitic granites intruded into Devonian-Carboniferous Amunike formation in a long strip fashion in the Huashigou
area. According to the zircon U-Pb weighted mean age of 252.0 ± 2.1Ma determined using LA-ICP-MS, it was suggested that the rock
was formed in late Permian. Monzonitic granites contain rich SiO2 (69.8%~72.2%) and Al2O3 (14.2%~15.4%), and low TiO2, MgO
(0.28%~0.36%, 0.60%~0.77%, respectively), with A/CNK=1.08~1.14, rich alkali (Na2O+K2O = 6.57%~8.00%), relatively enriched Th,
K, Pb, depleted Nb, Ta, P and Ti, low content of Sr (201×10-6~248×10-6), high content of Y (19.4×10-6~24.0×10-6), enriched LREE, (La/
Yb)N=10.8~18.4, moderate anomaly negative Eu (δEu=0.55~0.68); whole-rock (87Sr/86Sr)I=0.7060~0.7061, εNd(t)=1.63~1.84, and εHf(t)=
8.79. The Nd and Hf model ages of whole-rock of monzonitic granites are 780~794 Ma and 694 Ma, respectively. Overall,
our study shows that the Huashigou monzonitic granites is the product of partial melting of Mid-Neoproterozoic basaltic lower crust by
the underplating heating of late Paleozoic basaltic magma under the tectonic setting of orogenic compression transforming into post
orogenic extension.

Geochemical Characteristics of Argillaceous Rocks of the
Mesoproterozoic Bingmagou Formation in Yichuan, Western Henan
and Its Environment and Provenance

ZHENG Deshun，SUN Fengbo, CHENG Yong, ZHANG Feipeng

2016, 22(2):  254. 

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The Paleao-Mesoproterozoic tectonic and sedimentary evolution of southern North China craton has been debating for long
time, with controversies focusing on whether it is a subduction or cracking rift. As the first sedimentary layer formed after Xiong’er
Group, the Mesoproterozoic Bingmagou Formation is important to address this issue. Based on the analysis of geochemical
characteristics of REE and trace element of argillaceous rocks in Bingmagou Formation, the sedimentary environment and properties of
provenance and their tectonic significance were discussed in this study. The results showed that Chondrite normalized REE and trace
elements have a high differention between LREE and HREE, which showed anomaly negativeδ Eu, anomaly insignificantδ Ce, and enrich
Rb, Th, La, Ce, Nd, Zr, Hf, etc. Compared with the average upper crust, it was enriched in Sc, V, Cr , Co, Ni, Rb. Also we found that
Ceanom index and V/V+Ni ratio reflected a reduction argillaceous sedimentary environment, and Sr/Ba and B/Ga ratios indicate its

transitional environment from continent to marine. In addition, Cr/Zr, Th/U and other elements ratios prove its provenance is not deep
material, and La/Yb-Ce, Co/Th-La/Sc diagrams indicate the provenance is middle-acidic volcanic rocks. Furthermore, Th-Sc-Zr/10,
Th-Co-Zr/10 illustrations indicate its provenance is mainly from continental volcanic arc. Taken these results and regional geological
information together, it can be concluded that Bingmagou Formation in Yichuan was formed in an extensional back-arc basin, Xiong’er
Group was an arc islan

Spatial-Temporal Variation and Associated Driving Factors of pH
Values in Soils in the Past 30 Years in the Southern Jiangsu Province

SHAO Wenjing, SONG Yinxian, WANG Cheng, LI Wei, JI Junfeng

2016, 22(2):  264. 

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The Southern Jiangsu Province is one of the major Chinese grain-producing areas, where the quality of cultivated soil and
farm produce are significantly affected by the changes of soil pH values. Through the investigation of pH values of cultivated soils in theSouthern Jiangsu Province in 2010s, and comparing with two spatial distribution maps of soil pH in 1980 and 2003 from previousstudies, the spatial-temporal variation of pH values and associated factors have been discussed in this paper. The results showed that the spatial distribution pattern of soil pH in 2010s was significantly different from that in 1980, with lower soil pH values in the west part of the study areas than those in the east in 2010s, which is associated with natural conditions and social behaviors. Two phases of pH change have been observed in the context of complex changes in soil chemical properties during the past 30 years. The variation trends of pH values in different regions from 1980 to 2003 were similar to the major trends from 1980 to 2010s, while transformations have emerged in the last decade since 2003, especially presented in Jurong city where soil acidification has occurred in the later 10 years after alkalization in previous 20 years, and Suzhou-Wuxi Countries where it displayed the opposite trend. The decrease of pH values in soils can be explained by both heavy application of chemical fertilizers and industrial acid deposition. In addition, urbanization and cement production also played an important role in the pH increase. It is concluded that the different variations of pH values are caused by the waxing and wining of buffer substances in soil, which are mainly forced by the changes in land utilization in different regions.

Organic Carbon Isotope Stratigraphy of the Early Cambrian Huitong Section in Hunan Province, Southeastern Yangtze, China

WANG Dan, LING Hongfei*, ULRICH Struck, YAO Suping, LI Da, WEI Wei, WEI Guangyi

2016, 22(2):  274. 

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The early Cambrian is one of the critical periods during Earth evolution involving significant evolution of marine
environment and metazoans. However, the early Cambrian strata in the deep-water setting along the southeastern margin of the Yangtze Platform are still lack of systematically and accurately stratigraphic correlations. Here we conduct a high-resolution organic carbon isotope chemostratigraphy of the deep-water chert in the Liuchapo Formation and black shales in the Xiaoyanxi Formation, which werecollected from drill cores in the Huitong section of Hunan Province. Results indicate four positive δ13Corg excursions (termed P1, P2, P3 and P4 ) and two negative δ13Corg excursions (termed N1 and N2 ) in ascending order. Combined with the fossil records and zircon U-Pb dating data, we correlate the δ13Corg curve of the Huitong section with the δ13Corg and δ13Ccarb curves of other sections in Hunan and shallow-water areas including Yunnan and Three Gorges. The correlation implies that the Ediacaran-Cambrian boundary was placed at the negative δ13Corg excursion (Basal Cambrian Carbon isotope Excursion, BACE) in the upper Liuchapo Formation of Hunan Province. This negative δ13Corg excursion (BACE), however, has not been identified at the Huitong section, owning to the limited drill core depth.
The three positive δ13Corg excursions P1, P2 and P3 can be correlated with ZHUCE (ZHUjiaqing Carbon isotope Excursion, Stage 2),
CARE (Cambrian Arthropod Radiation isotope Excursion, Stage 3) and MICE (Mingxinsi Carbon Isotope Excursion, Stage 4) δ13Corg
excursions, respectively. In contrast, the two negative δ13Corg excursions N1 and N2 are likely correlated with SHICE (SHIyantou Carbon
isotope Excursion, Stage 2) and AECE (Archaeocyathid Extinction Carbon isotope Excursion, Stage 4) δ13Corg excursions, respectively.
Therefore, the upper Liuchapo and the basal Xiaoyanxi formations probably belong to the Cambrian Stage 2. The lower Xiaoyanxi
Formation belongs to the Cambrian Stage 3 and the middle-upper Xiaoyanxi Formation belongs to the Cambrian Stage 4. However, it is
still unclear whether the top of the Xiaoyanxi Formation covers the end of the Cambrian Stage 4. The negative δ13Corg excursions
probably result from the transportation of 12C-enriched anoxic bottom water through upwelling from deep to shallow water, and might be
closelyassociatedwiththemassextinctionofEdiacaranfauna,smallshellyfossilsandarchaeocyathids.Incontrast,theflourishofCambrian
faunacouldincreasetheprimaryproductivityandassociatedrateoforganicmatterburial,whichleadtothepositiveδ13Corg excursions.

Macroscopic and Spectroscopic Study on Fluoride Sorption by HAP

REN Chao, WANG Hongtao*, JI Junfeng, LI Wei*

2016, 22(2):  289. 

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Geologic fluoride pollution is a worldwide environmental problem, as numerous countries and regions are facing problems
that drinking water contains excess F concentration. In this research, we adopted low-cost non-metal mineral hydroxyapatite (HAP) as adsorbent to study the geochemical behavior and mechanism of F adsorption as a function of reaction time, pH, and initial F concentration. After 48 hours, the reaction reached equilibrium and yielded a maximum adsorption amount of 21.6 mg/g at pH 6 through regression analysis using Langmuir equation. To further understand the mechanisms of F adsorption on HAP, we employed advanced geochemical approaches, such as XRD, SEM, HR-TEM, and 19F solid state NMR, to characterize the sorption products before and after reaction. It can be concluded that formation of F-Hap (s) solid-solution is the dominant mechanism at high F initial concentration (>10 ppm). This study demonstrates that hydroxyapatite is a good candidate material for fluoride removal.

Gravity and Magnetic Anomalies and Their Relation to the Metallogenic Belt in the Central Segment of the Qinling Orogenic Belt

AN Shaole，YUAN Bingqiang，ZHANG Chunguan，SONG Lijun

2016, 22(2):  299. 

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Distribution of metallogenic belt is controlled by geological structures that can be delineated by gravity and magnetic
anomalies. In order to study the relationship between gravity, magnetic anomalies and mineralization belt in the central segment of the Qinling orogenic belt , we collected and processed the gravity and magnetic survey data of the Qinling orogenic belt. We also analyzed and interpreted the distribution characteristics of gravity and magnetic anomalies and inferred fault structures in the study area. In addition, we discussed the undulation characteristics of crystalline basement and the connection among gravity and magnetic anomaly characteristics, geological structures and metallogenic belt, together with regional geology and deposit distribution. This study shows that most of the deposits are located within zones of high gravity and magnetic anomaly gradient or intersections of several groups of anomalies in different orientations, especially in local high gravity anomaly range and along edges of a gradient belt. The results of this research are useful for studying geological evolution of the Qinling orogenic belt, geological structures (especially in deep structures),fracturedistribution.Thefindingswillalsoprovideanimportantreferenceforpredictingfavorableareasofmineralization .

Two kinds of Shear Senses and Tectonic Implication of the Jingdezhen Ductile Shear Zone, Northern Jiangxi Province

XU Xianbing, TANG Shuai, Lin Shoufa

2016, 22(2):  308. 

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The Jingdezhen ductile shear zone is located at the core of the Neoproterozoic Jiangnan Orogen. Structural features and
geochronology of the Jingdezhen ductile shear zone have a key implication for the Neoproterozoic to Early Paleozoic tectonic evolution of the South China Block. The Jingdezhen ductile shear zone is ~180 km long in the NE-striking orientation and ~7 km in maximum width. Two-phase ductile strike-slip shearing was identified based on detailed field investigation and observation of oriented thin sections. Moreover, the kinematic indicators and temperature-pressure conditions were studied in this paper. The early sinistral ductile strike-slip with thrusting occurred at 400~500℃ and differential stress of 40~300 MPa, whereas the dextral ductile shearing at 300~400℃ and differential stress of 120~300 MPa. Combined with the previous work, the sinistral strike-slip with thrusting of the Jingdezhen ductile shear zone took place at late stage of the Neoproterozoic orogen in the South China Block (810~800 Ma), as a result of transformation from syn-orogeny compression to post-orogeny extension. The dextral shearing of the Jingdezhen ductile shear zone occurred in the Early Paleozoic, triggered by the Early Paleozoic intracontinental orogeny of southeast China

Development Characteristics of the Cenozoic Fault System and Basin Evolution of Bonan Area in Bohai Sea

LIU Chao，LI Wei，WU Zhiping，ZHANG Xiaoqing，CHEN Xingpeng，LI Chunrui

2016, 22(2):  317. 

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Abundant 3D seismic data were used, combined with the characteristics of seismic profile and time slices, the fault
development and basin structure of Bonan area were researched. Furthermore, characteristics of the fault system and the structural evolution were delineated. The Cenozoic Tanlu fault in Bonan area was divided to eastern, middle and western branches. These branches interact with the EW-trending, NW-trending and NE-trending were associated with the strike-slip movement of the Tanlu fault, leading to the formation of the grid structural pattern in Bonan area due to changing stress field. There fore, changes in the relative importance between extension and strike-slip occurred in Bonan area. The Cenozoic structural evolution can be classified into three evolutionary stages, i.e., left lateral slip with strong extension, right lateral slip with strong extension and weak slip and weak extension. During the first stage of Ek-Es4, the Eastern Branch moved greatly but the Middle and the Western Branch weakly. The EW-trending, NW-trending controlled the basin pattern of the Huanghekou Sag and Laizhouwan Sag. During the second stage of Es3-Ed, three branches of the strike-slip fault and the main faults of other directions became activated. The secondary faults of the NE-trending and the near EW-trending faults began to develop. The two basins underwent persistent extension and rift. During the third stage of Ng-Nm, right-lateral strike-slip changed to weak, en-echelon faults of the NE-trending faults that appeared near the Middle and Western Branch, and secondary faults were increasingly developed. Two basins were transformed into initial rift.

Structural Characteristics and Main Controlling Factors of Hydrocarbon Accumulation of the Lower Permian Post-salt and Pre-salt Sequences in the Pre-caspian Basin

LI Feng, YIN Jinyin, YANG Yuanyuan, LI Zhao, SHI Lei

2016, 22(2):  327. 

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The Pre-caspian Basin is typically characterized by hydrocarbon accumulation in two salt-related sequences, i.e., the
post-salt and pre-salt sequences divided by the Lower Permian Kungurian Group. To improve the understanding of the regularities of hydrocarbon accumulation and provide exploration stratedy data, this paper studies the structural characteristics and controlling factors of hydrocarbon accumulation in the two post- and pre-salt sequences by using the latest data of drilling, seismic section interpretation and structural mapping. Results show that large-scale paleo-uplift and slope were developed in the Paleozoic pre-salt sequence and the Hercynian weathering and leaching greatly improved carbonate reservoir properties. Reef, shoal and karst controlled hydrocarbon accumulation. In contrast, the Lower Permian post-salt sequence was significantly controlled by the lower Permian Kungurian tectonic movement, leading to the formation of different types of traps, such as salt diapir, salt eave, stratigraphic pinchout and sandstone lens body. The highly-efficient salt windows, salt flanks and fractures are the key factors controlling hydrocarbon migration. Favorable match between salt tectonic activity and peak hydrocarbon expulsion of source rock is necessary for hydrocarbon accumulation.

Characteristics of Microscopic Pore Structures and Their Effect Impacts on Methane Adsorption Capacity in Continental Shales

CHEN Lei, JIANG Zhenxue, JI Wenming, CHEN Weitao, WANG Pengfei

2016, 22(2):  335. 

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Characteristics of microscopic pore structures of shales have important impacts on the assessment of gas and associated oil/gas
potential adsorption capacity of the shales, and previous studies have mainly focused on marine shales. Here, we conduct a pilot study of continental shales based on a case study of the fifth member of the Upper Triassic Xujiahe Formation in the western depression, Sichuan Basin. The microscopic pore structures of the shales were investigated by using low-temperature nitrogen gas adsorption method. Multiple structural parameters of the shales were calculated, including the specific surface area, pore size distribution, pore volume and average pore diameter. Then, high-pressure methane adsorption analysis was conducted to obtain the parameters of Langmuir volume and Langmuir pressure. Finally, we address the effect of microscopic pore structure characteristics on the methane adsorption capacity of the shales. Results show that the average pore diameter of the shales ranges from 7.81 to 9.49 nm. Mesopores dominate in the shales, while some micro- and macro-pores also exist. Slit-like pores are the main pore types in shales, and a small amount of ink-bottle-like pores are also present. The specific surface area of the shales are much greater than that of conventional reservoir rocks; this is good for gas adsorption in shales. The mesopores with the pore diameter between 2 and 50 nm provide the dominating pore volume, which constitutes the major space for gas adsorption and storage in the shales. Under the temperature condition of 85 ℃, the Langmuir volume of methane adsorption in shales ranges from 1.21 to 4.99 m3/t, and methane adsorption capacity varies largely within different shales. There are positive correlations between Langmuir volume and specific surface area of shales, and between specific surface area and clay minerals content of shales. However, no correlation exists between specific surface area and TOC of shales. There are positive correlations between Langmuir volume and micropore and mesopore volume. Organic matter is an important control on micro- and meso-pores of shales, evidenced by the positive correlations between micropore and mesopore volume and TOC. Comparatively, clay minerals play a much more important role on the pore volume of micro-and meso-pores of shales. For continental shales, organic-matter thermal evolution is relatively low and organic pores are thus not well developed. In contrast, abundance of clay minerals is relatively high in shales, with well development of micropores and mesopores, which constitute a considerable specific surface area of shales and thus affect the methane adsorption capacity of shales.

Organic Matter Characteristics in Longmaxi Formation Shale and Their Impacts on Shale Gas Enrichment in Southern Sichuan

PAN Tao, ZHU Lei, WANG Yadong, LI Xiaomeng

2016, 22(2):  344. 

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Multiple sets of marine mud and shale in the Lower Paleozoic Cambrian were widely developed in the southern part of
Sichuan basin. As a set of good hydrocarbon source rock in Sichuan basin, the Longmaxi Formation has the potential to produce good quality shale gas. Based on the drilling data, core samples, outcrop data and geochemical experimental analyses of core samples of ChangNing and Weiyuan region, we have researched lower Silurian Longmaxi organic matter characteristics and their impacts on the enrichment regularity of shale gas. The results showed that the main types of organic matter are type I and II1 in the study region. Organic carbon content is very high (average TOC=2.52%), and the thermal evolution level is high (Ro=2.1%~3.5%). The organic matter has strong influence on the enrichment of shale gas. Kerogen type determines the methane adsorption capacity, the organic carbon content, and thermal evolution level determines the amount of product and the content of gas in the shale. Also, the high TOC and Ro can promote organic micro pore growth to increase more favorable space for the enriched shale gas. On the whole the Longmaxi Formation has a superior organic matter characteristics that strongly influence shale gas enrichment.

Migration Pathway System of the Reservoir in Shawan Formation in Chepaizi Salient, Junggar Basin

WANG Kun, REN Xincheng, MA Kui, HUANG Qingyu, SHI Shuyuan, GAO Jianwen

2016, 22(2):  350. 

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The Neogene Shawan formation is one of the important hydrocarbon-rich strata in Chepaizi salient. Based on the analysis of
reservoir distribution and oil nature, coupled with results of previous studies, the accumulation process of Shawan hydrocarbon is
divided into two stages: paleoreservoir stage and secondary adjustment stage. The migration pathway systems and their spatial
combinations are discussed. In the paleoreservoir stage, the Cretaceous basal unconformity and syngenetic reverse faults composed the migration pathway in the Hongche fault zone formed system. The effective thickness of migration zone in the unconformity is thicker in the northern and estern part of the research area while pinching out toward the west; syngenetic reverse faults controlling the formation and development of Hongche fault zone have large fault displacements and beneficial for hydrocarbon migration. In the secondary adjustment stage, sandstone in the first member of Shawan Formation (N1s), epigenetic normal faults in Hongche fault zone, Aika fault zone and Neogene normal fault in Chepaizi salient formed the migration pathway system, the N1s sandstone salient with continuous and stable deposition distributes in the Chepaizi, blanket-like pinching out from the south to the north. As the lowest sandstone bed, the blanket-liked sandstone is the most important transverse migration bed in this stage. Large-scale normal faults in the Hongche fault zone were developed in the late Neogene; Normal faults in the Chepaizi salient were also developed in the same period; the Aika fault zone continued to be active in the Neogene, all of which formed the vertical migration pathway system in the secondary adjustment stage. The dominant migration zones of the Cretaceous unconformity and blanket-liked sandstone migration beds are predicted using
migration pathway index (MPI) and Quantitative Grain Fluorescence (QGF). In the plane, area with MPI greater than 0.3 is regarded as
the dominant migration zone of unconformity migration bed and the area with QGF greater than 3.8 is regarded as the dominant
migration zone of N1s blanket-like sandstone. Based on the analysis of spatial combination of migration pathway systems in different
stages and the relationship between hydrocarbon distribution and migration pathway systems, the control action of migration pathway
system on hydrocarbon accumulation is confirmed prospecting to have. The well P609 area is predicted to have advantages of
hydrocarbon migration, which can be regard as the exploration target of further prospecting.

Controls of Multistage Slope Breaks on the Hydrocarbon Traps in Beixi Slope of Hailaer Basin

WANG Xiabin，JIANG Zaixing，YUAN Shuai

2016, 22(2):  360. 

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The lithologic-stratigraphic traps in lacustrine basins are controlled by slope-breaks. Beixi Slope in Hailaer Basin has the
characteristics of slope-breaks. It is important to study the features and genesis of slope-breaks, and the control mode of sedimentary facies and lithologic-stratigraphic traps to help identify favorable exploration area. By the genetic mechanism of Beixi slope-breaks, we can divide them into fault slope-break, flexural slope-break, sedimentary slope-break and erosive slope-break. According to the relationships between slope-break and subsag, we divide the slope-break into three cells-inner slope-break, middle slope-break and outer slope-break. The outer slope-break is characterized by erosion slope-break, controlling the stratigraphic overlap traps; the middle slope-break is mainly fault slope-break and flexural slope-break, controlling the block-lithologic combination traps; the inner slope-break is mainly sedimentary slope-break, controlling the lenticular lithologic traps.

A Comparative Study on Whole-aperture Pore Structure Characteristics between Niutitang and Longmaxi Formation of High-matruity Marine Shales in Southeastern Chongqingelt

YANG Xiao, JIANG Zhenxue, SONG Yan, HUANG Hexin, TANG Xianglu, JI Wenming,

2016, 22(2):  368. 

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The marine organic-rich shales of Niutitang and Longmaxi formation in south China became the key horizons for shale gas
exploration. But the thermal evolution degree of the shales is very high and its pore structure is complicated. In order to deepen the understanding of this complexity, we analyzed the whole-aperture pore structure characteristics of two sets shales using a combination of field-emission environmental scanning electron microscope (FEI-SEM), high-pressure mercury injection and low-temperature gas (N2 and CO2) adsorption experiments. Results show that the pore volume of the Niutitang and Longmaxi formation were in the range of 0.0202~0.0402 mL/g and 0.0255~0.0310 mL/g, respectively. Mesopores had the largest proportion in two sets of shale pore volume. The average specific surface area of two sets shales were in the range of 13.74~41.26 m2/g and 21.42~27.82 m2/g, respectively. Micropores and mesopores amounted to almost 95% of the specific surface area in shale. The pore structure characteristics of two sets shales were very different. The dissolution pores and interparticle pores were developed in the Niutitang formations while organic-matter pores were unevenly distributed. And organic-matter pores, interparticle and intraparticle pores in the mineral matrix were well-developed in the Longmaxi formations. Micropores in the Niutitang formations were well-developed while mesopores and macropores in the Longmaxi formations were better developed. According to the result of the experiment data and past literature, the level of maturity and buried depth played a decisive role in the difference of pore structure characteristics.

Heterogeneity and Significance of Coal Reservoir of Upper Paleozoic in Southeast Margin of Ordos Basin

YI Wei, XIONG Xianyue, PANG Bin, WANG Wei, LIN Wei, HE Chunlian, CHE Yanqian, FE

2016, 22(2):  378. 

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A number of high-yield wells has emerged in the southeast margin of Ordos Basin, which showed the potential of the Upper
Paleozoic exploration and development of coalbed methane resources. However, owning to the coal reservoir heterogeneity, great
differences of individual gas wells were observed in adjacent block groups and sometime even in the same block. Therefore, a deeper understanding of reservoir heterogeneity is needed for efficient exploration and development. Systematic studies were conducted on coal reservoir in terms of rock characteristics, physical characteristics, adsorption characteristics, and gas characteristics. The results showed that the 3, 5, 11 coal seam, with stable distribution and large thickness, is the main target for exploration and development of coalbed methane. Half-bright coal seam and semi-dark coal with high vitrinite content has better fracture resistance, whereas a low ash-lean coal was also found, with anthracite and a small amount of high grade coal identified in some sections. We found that coal rock porosity and permeability are low, showing strong adsorption, short adsorption time and the higher desorption rate. This is conducive to CBM output, however, coal measures of reservoir stimulation need to be strengthened. The average gas content is about 11 m3/ t or more, with a maximum of 19.73 m3/ t, and the average gas saturation is above 61%, indicating a greater resource and a high density of formation energy, in favor of CBM desorption output.

Microbial Mats and Mineral Microstructure Features of Meso-Neoproterozoic Ruyang and Luoyu Group in Lushan Area

ZHENG Wei, YUAN Yuyang, XING Zhifeng*, QI Yon

2016, 22(2):  385. 

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Microbially Induced Sedimentary Structures (MISS) rise from the interaction of benthic microbiota with physical sediment
dynamics. It was the important product and geological record in clastic sediments of microbial community activity. Research on MISS is of great significance for understanding evolution of earth-surface environment, because MISS was widely found in terrigenous fragmentary rock of Precambrian and was occasionally distributed in Phanerozoic. Based on observation, description and genesis of outcrops, the MISS in Lushan area can be divided into three types: Mat growth feature, Mat destruction feature, and Mat decay feature. With the aid of micromorphological observation, we analyzed and discussed morphological feature, geologic structure, components, genesis and sedimentary environment of MISS. Based on microscopic analysis for quartz grain and composition characteristic of MISS, we found that microbial community develop in the relatively high-energy and fine-grained sediments environment. Therefore, we conclude that MISS mainly developed near intertidal zone to supralittoral zone. This research will contribute to the discrimination of the paleocurrent direction, intensity and ionic content, and can also help reconstruct paleoenvironment to a certain extent.

Application of Mass Flux in the Assessment of Natural Attenuation of BTEX and Ethanol in Groundwater

JIANG Lingzhi, CHEN Yudao*, DENG Chaolian, JIANG Yaping

2016, 22(2):  395. 

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In recent years, application of the Monitoring Natural Attenuation (MNA) method in petroleum hydrocarbon removal from
groundwater was widely studied. Alternatively, mass flux calculation becomes an important way to evaluate the remediation effect of MNA on removing gasoline pollutants in groundwater. In this study, ethanol and BTEX from gasoline, associated with bromide as a non-active tracer, were injected into a sand tank and their degradation was monitored. Based on mass flux method, mass reduction rates and first-order natural attenuation rate constants of BTEX and ethanol were obtained. The results showed that the mechanism of nature attenuation is important for removing fuel components in groundwater, and mass flux is an effective method to evaluate the nature attenuation, with the removal rates of BTEX and ethanol in natural attenuation to be 78.88% and 98.71%, respectively. About 98% of BTEX was removed by adsorption and intrinsic biodegradation as well as approximate 100% ethanol removed by intrinsic biodegradation. The first-order natural attenuation rates of BTEX ranged from 0.077 d-1 to 0.167 d-1. Compared with BTEX, ethanol had a larger rate (0.353 d-1), indicating that ethanol was more rapidly to be attenuated than BTEX under natural condition.