• Volume 40,Issue 4,2013 Table of Contents
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    • The major chromium concentration areas in China and a discussion on their resource potential

      2013, 40(4):995-1006.

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      Abstract:Abstract:Chromium is one of the most scarce mineral resources in China. For a long time, its need has been mainly met by imports, and it is very difficult to guarantee the security of resources. China has hence attached great importance to the chromite ore prospecting. Since 2006, China Geological Survey has implemented the plan of potential evaluation for 25 kinds of important mineral resources, including Cr. Based on the research on the metallogenic regularity of chromium, this paper preliminarily assigned chromium deposits in China to 12 large ore concentration areas. Meanwhile, based on the most recent progress and data obtained in recent years, the authors hold that Lhobasar, Dalabute and Hegenshan areas are the most important concentration areas in China. This paper describes the three most important ore concentration areas in detail, and discusses their resource potentials separately.

    • Zircon SHRIMP U-Pb dating of basalt from Huangshuihe Group on the western margin of the Yangtze block and its geological significance

      2013, 40(4):1007-1015.

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      Abstract:Abstract:The structural clip of Huangshuihe Group, distributed along Longmenshan thrust nappe belt, is one of the typical low-grade metamorphic rock series, and some metamorphism could reach amphibolite facies, with the wide distribution of volcanic rocks. Based on field geological survey in combination with petrologic and petrographic analysis, the authors collected a sample of basalt from Ganheba Formation for zircon SHRIMP U-Pb dating, and obtained two U-Pb 206Pb/238U weighted average ages of (799±8) Ma (MSWD=0.96) and (875± 12) Ma (MSWD=0.38). The former age of (799±8)Ma represents the crystallization age of the basalt, suggesting Mid-Neoproterozoic, whereas the latter represents the age of captured zircon, signifying a tectonic-magmatic event of Jinning movement. Combined with the results of data obtained from the region, the authors hold that Huangshuihe Group, Yanjing Group, and Suxiong Formation were contemporary sedimentary strata formed in the late Qingbaikou period.

    • Zircon LA-ICP-MS U-Pb age of Caledonian granites from Precambrian basement in Yunkai area and its geological implications

      2013, 40(4):1016-1029.

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      Abstract:Abstract:LA-ICP-MS U-Pb dating was conducted for zircons from four gneissic granites in Yunkai area, which were assigned to Precambrian basement rocks or Neoproterozoic intrusion in 1∶250000 geological survey. The dating yielded 206Pb/238U weighted mean of 443.3±2.6 Ma (sample 1009, Lutou Reservoir in Luchuan City), 445.7 ±2.3Ma (sample 1010, Yuedong in Luchuan city), 441.1±2.0Ma (sample 1012, Xieji in Gaozhou city) and 443.7±1.7Ma (sample 1018, Zhusha in Xinyi city), suggesting that these rocks are Caledonian products rather than Precambrian basement or Neoproterozoic intrusive rocks. In combination with previous studies, the authors hold that these granites probably resulted from partial melting of the Proterozoic materials due to the Caledonian orogeny in South China. These results and recently published data (Caledonian) for the so-called Precambrian basement rocks, such as the crystallization age or metamorphic age of gneissic granite and gneiss, indicate that Yunkai area has undergone extensive reformation by the Caledonian orogeny. Actually, the Precambrian basement of Yunkai area mainly consists of gneissic rocks and meta-sedimentary rocks, which serve as the representative of the Gaozhou complex and the Yunkai Group, respectively. The Gaozhou complex was formed during the Meso- to Neo-proterozoic and the Yunkai Group might have been formed in the Neoproterozoic. The Paleo- to Meso-Proterozoic crystallized basement does exist in Cathaysia Block, however,which is not so widely distributed as previously thought.

    • Age, geochemical features and Cu-Au mineralization significance of the magnesian dioritic dykes in Baogutu area of west Junggar

      2013, 40(4):1030-1043.

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      Abstract:Abstract:The magnesian dioritic dykes widely distributed in west Junggar of Xinjiang recorded the Late Paleozoic tectonic evolutionary history of the area. The LA-ICP-MS zircon U-Pb and amphibole Ar-Ar dating of dioritic dykes yielded a 206Pb/238U age of 316.3±3.8 Ma and a plateau age of 313.1±3.5 Ma, respectively, suggesting that they were generated in Late Carboniferous. The magnesian dioritic dikes (56.8%-62.9%) are characterized by high MgO (2.39%-4.04%; Mg#= 54-62), Cr (30×10-6-80 ×10-6), and Ni (20×10-6-62×10-6) content. These samples show negligible to negative Eu values, high Sr/Y (36-44) ratios, strong depletion of HREE (e.g., Yb = 1.32×10-6-1.54×10-6 and Y=13.1×10-6-15.5×10-6), and enrichment of large-ion-lithophile elements (LILE) (K, Sr, Ba) with negative Nb-Ta-Ti anomalies. These features are compatible with slab-derived adakites interacted with mantle materials and related to ridge subduction. The interaction between high oxygen fugacity slab melt and mantle peridotite caused the decomposition of metal sulfides and the Cu and Au mineralization. Baogutu area of west Junggar thus has good metallogenic prospect.

    • Late Triassic magma mixing in the East Kunlun orogenic belt: A case study of Helegang Xilikete granodiorites

      2013, 40(4):1044-1065.

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      Abstract:Abstract:In the East Kunlun orogenic belt (EKOB), mafic microgranular enclaves (MME) occur frequently in Late Permian-Triassic granitic rocks. In this paper, the authors took Helegang Xilikete granodiorites in the eastern part of the EKOB as an example to study their host rocks and MME in detail. Characteristics of the host rocks and the MME, such as field occurrence, morphology, texture and structure and mineralogy, together with the geochemistry, show that they were cooled and crystallized in a short time immediately after the intrusion of basaltic magma into intermediate-acidic magma and thus have similar distribution patterns to the host rocks in the REE diagram and trace element spider diagram, such as the enrichment of the LREE and LILE and the depletion of the HREE and HFSE, reflecting a typical feature of magma mixing. The result of LA-ICP-MS zircon geochronology implies that the crystallization age of the MME is about 224.9±4.1 Ma, very close to that of the host rock (225±5 Ma), suggesting a crust-mantle magma mixing event at the stage of post-collision in the EKOB in Late Triassic.

    • The gravity field evidence of the existence of a group of NNW-SSE trending fracture structures on the western margin of Qaidam Basin

      2013, 40(4):1066-1078.

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      Abstract:Abstract:The western margin area of Qaidam Basin is close to the juncture between Altun orogen and Qimantag orogen of East Kunlun, where the tectonic movement is very complex. Based on a study of the newest data obtained from 1∶250000 gravity survey, the authors recognized a group of new NNW-SSE trending faulted structures, in addition to NEE-trending Altun fractures and NWW-nearly EW-trending South Kunlun, Central Kunlun and North Kunlun fractures. In this paper, the authors provided gravity evidence for the existence of a group of NNW-SSE trending fractures in this region. Based on an analysis of their characteristics and origins, the authors consider that these fractures are a group of newly rifted strike-slip structures, which have high-angle right-lateral fractures characterized by small fault displacement and long stretches, and they pass through the high-angle right-lateral fractures, belonging to a group of NEE and NWW-nearly EW trending fault zones. Further studies show that these fractures are a group of new faulted zones related genetically to NE-trending movement of the whole Tibetan Plateau. The new findings may have some significance for the understanding of the tectonic movement (especially the new tectonic movement ) and the mineral research in Qaidam western margin area.

    • Nature, origin and tectonic setting of Jinzhou basin in the south segment of Xuefeng orogen

      2013, 40(4):1079-1091.

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      Abstract:Abstract:Jinzhou basin is a small NE-trending Late Triassic-Middle Jurassic continental basin in the south segment of Xuefeng orogen. Previous researchers held that the basin is a pull-apart extensional basin related to dextral strike-slipping of NNE-trending Xupu-Jinzhou fault. The authors studied the tectonic characteristics, sedimentary features and proto-basin of Late Triassic-Middle Jurassic Jinzhou basin and, on such a basis, brought forward the opinion that the basin is a compressional quasi-foreland basin according to evidence as follows: ① High maturity of the deposits and the harmony of the basin boundary with surrounding older geological boundary indicates that the basin is a compressional low depression. ② High component maturity and far-resource features of the deposits suggest that the basin was formed in a stable tectonic setting. ③ The sedimentary space of Upper Triassic-Lower Jurassic strata in the northern basin was formed from rocks bending. The attitude changes of rocks indicate that the basin was NW-compressed and folded in Middle Jurassic. Sedimentary features show that there existed shallow- and deep-water environment in the west and the east of the basin, respectively, which implies that the basin was controlled by gravity load of east peripheral thrust block. ④ In adjacent areas of the basin, there occur a few extensional faults and a lot of small strike-slip faults, thrust faults and conjugated shear joints related to the compression. ⑤ According to the strike deflexion of the fault, Jinzhou basin was situated in a compressional area instead of an extensional area when Xupu-Jinzhou fault experienced dextral strike-slipping action. Based on the sedimentary and tectonic characteristics of Jinzhou basin and the regional tectonic setting, the authors hold that the basin was related mainly to regional S-N-compression during Late Triassic-Early Jurassic period, and related to NWW-compression and NNE-trending dextral strike-slipping during Middle Jurassic period.

    • The origin of lakes in Beijing City

      2013, 40(4):1092-1098.

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      Abstract:Abstract:Beijing, as the capital of China, is well-known for plenty of lakes in its historical period. The distribution and origin of these lakes are highly controlled by the geological structure of Yongding River alluvial fan. By analyzing the type of sediment distribution, the characteristics of structure and the locations of present lakes, this paper deals with the distribution regularity of these lakes. There exists a clear geological boundary, as shown by the differences of geological structures. The western part of Beijing plain is a single gravel layer rich in underground water, while the eastern part is mainly of the clay-interbedded-with-silt water retaining structure poor in underground water. Lakes are divided into different genetic types by the geological boundary. The most western lakes, such as Kunming Lake, Fuhai Lake, Zizhuyuan Lake, Yuyuantan Lake, Lianhuachi etc., are dominated by the spring and depression genesis, whereas the lakes in the eastern part are dominated by residual water bodies of the old channel of the Yongding River. Studies show that geological structures are the main control factors for the distribution of lakes in Beijing City with certain regularity, and that urban planning and construction should follow the natural law. The results obtained by the authors have important significance for urban development, disaster prevention and reduction as well as rational utilization of water resources.

    • Reconstruction of the late Sinian paleo-ocean environment in Sichuan basin and its geological significance

      2013, 40(4):1099-1111.

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      Abstract:Abstract:On the basis of carbon and oxygen isotopic compositions of 69 dolomite samples collected from three sampling points of the Sinian Dengying Formation in Sichuan basin and the effectiveness evaluation of the data, the authors studied the changing characteristics of carbon and oxygen isotopes with the purpose of further reconstructing the corresponding paleo-ocean environment and investigating its geological meaning. The δ13C values of dolomite in Dengying Formation vary from -2.85‰ to 4.44‰ with a mean value of 1.80‰ and the δ13Cvaries vary between -9.02‰ and -1.90‰, -5.42‰ on average. The changing trends of the carbon and oxygen isotopes are similar to those in other strata of the same period in the Yangtze platform. Through the reconstruction of paleo-ocean environment, the authors found that the Sichuan basin of Late Sinian Dengying period was in a marine environment, and the seawater temperatures varied mainly between 15℃ and 30℃, suggesting a warm or hot subtropical climate. The sea level experienced six stages in Dengying period in the study area, i.e., slow transgression, lowstand oscillatory regression, highstand oscillatory regression, transient transgression, sustained regression and oscillatory regression. Under the influence of sea level fluctuation, climate change, tectonic movement and volcanic activity, four negative δ13C anomalies (N1~N4) and two positive δ13C anomalies (P1~P2) occurred in dolomite of Dengying Formation. The basin was filled with easily-recognized grape-sized algal dolomite in Deng2 Member, dark clastic rock in Deng3 Member and algal dolomite in Deng4 Member because of the influence of the paleo-ocean environment.

    • Geochemical characteristics and sedimentary-tectonic setting of the Cambrian sandstones and mudstones in Dayaoshan-Damingshan area,Guangxi

      2013, 40(4):1112-1128.

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      Abstract:Abstract:The Daoyaoshan-Damingshan area is located in the southwestern section of the Qinzhou-Hangzhou juncture between the Yangtze Block and the Cathayian Block.The study of the early Paleaozoic sedimentary environment and tectonic setting of this area is a key to understanding the geotectonic problems in South China. Major and trace elements of 27 pieces of samples from Cambrian sandstones and mudstones in this area were analyzed and discussed. The samples generally have high ratios of Al2O3/TiO2 ( in the range of 11.95~36.26,20.81 on average) and lower ratios of Rb/Cs(in the range of 13.02~68.27, 32.21 on average) and Cr/Zr(ranging 0.14~1.15,averagely 0.59). Geochemical characteristics, such as the plots of Ni-TiO2,Th/Sc-La/Sc and La/Th-Hf , indicate that the Cambrian sediments in the Daoyaoshan-Damingshan area were mainly sourced from the upper crustal felsic quartz rocks,with the addition of a small amount of igneous sources and ancient recirculation sediments.The distribution of trace and rare-earth elements and the data of La-Th-Sc,K2O/Na2O-SiO2, δCe,δEu,Tb/Yb,La/Sc,La/Th,Th/U as well as the comparison with different tectonic settings show that the study area belonged to a passive continent-marginal setting. In addition, such evidence as the marks of shallow-sea deposits,the data of sedimentary palaeogeography,regional geology and geochemistry suggests that during the Early Paleozoic there existed no geochemical evidence for the so called “ancient ocean in South China”.

    • A discussion on the sedimentary environment of Shibantan Member of Dengying Formation in the eastern Yangtze Gorges area

      2013, 40(4):1129-1139.

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      Abstract:Abstract:Based on a detailed study of the rock constituents and sedimentary structure of the typical sediments, the authors found that the depositional?environment?of the Shibantan Member of Dengying Formation was a platform edge shallow - platform margin ramp. According to the outcrop sections and the observation, the authors recognized many depositional characteristics of storm deposits, such as hummocky cross stratifications, scouring-filling structures,graded bedding and convolute bedding. The environment of the Shibantan Member of Dengying Formation was influenced by periodic strong waves or storms, occurring below the normal wave base and above the storm wave base.

    • The types and evolution of platform-edge reefs in Permian Changxing Formation,eastern Sichuan Basin

      2013, 40(4):1140-1149.

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      Abstract:Abstract:The formation, development and consumption of Kaijiang-Liangping trough have obviously controlled the distribution of Changxing Formation reefs, and thus determined the types, sizes and distribution of the reef gas reservoirs. Through the detailed study of internal structures and their development, the authors found that the platform-edge reefs have very different sedimentary characteristics in different places near the trough, and could be divided into patch reefs, mound reefs and barrier reefs according to the development scales. The platform-edge reefs and their evolutionary stages were summarized systematically. The patch reefs were mainly developed from Changxing 1st period or Changxing 2nd period to Changxing 3rd period on the southern side of Kaijiang-Liangping trough, characterized by the shortest formation time, the smallest scale, the most simple texture and three evolutionary stages. The mound reefs were mainly developed from Changxing 2nd to Changxing 3rd period on the middle to northern side of Kaijiang-Liangping trough, and their development could mostly last to the Changxing 3rd period, with the characteristics of larger scale, more complex texture relative to the patch reef, and five evolutionary stages. The barrier reefs were mainly developed from Changxing 1st to Changxing 2nd period at western Hubei trough or in east Sichuan area, and their development mostly lasted to Changxing 3rd period, with the characteristics of longest formation time, largest scale, most complex evolution and five evolutionary stages.

    • The Ying 26 fault accommodation zone and its control effects on hydrocarbon distribution in Dongying sag

      2013, 40(4):1150-1158.

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      Abstract:Abstract:To reveal the characteristics of the fault accommodation zone and interpret its control effects on hydrocarbon distribution in the complex fault block oilfield, the authors conducted the study of faults geometry, kinematics and dynamics in Ying 26 block using 3D high-precision seismic data together with oil field geological data, and discovered that it is a typical EW-striking convergent-overlapping and synthetic-overlapping compound fault accommodation zone. The section structural patterns of the west-side major fault (Ying 1 fault) and adjustment faults are of the multiple-stage reverse Y style, and the east-side major faults (Ying 8 fault, Ying 31 fault) and adjustment faults are of the cabbage-appearance style. When the activity of Ying 1 fault became weak, the displacement accommodated Ying 8 fault, Ying 31 fault and adjustment faults, which made the total throw change regularly. The stress field of Ying 26 accommodation zone was complex: the northern part was left-lateral extension-tensional and the southern part was right-lateral extension-tensional. Through the analysis of distribution and source of Ying 26 block structure, characteristics of fault activities and fault sealing properties, the authors recognized the accumulation model of Ying 26 fault accommodation zone. The major fault was an oil source fault which connected the source kitchen and the reservoir, and hydrocarbon migrated during the main hydrocarbon accumulation period, whereas adjustment faults stopped activities in the earlier period, formed fault traps, and became barrier faults. The authors have constructed the reservoir forming model of Ying 26 fault accommodation zone, and pointed out that Ying 13 well, Ying 24 well and Ying 26 well areas are areas favorable for progressive exploration and development.

    • The distribution of Chang-8 tight sandstone oil reservoir of Yanchang Formation in Wubao area, central-south of Ordos Basin

      2013, 40(4):1159-1168.

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      Abstract:Abstract:Chang-8 oil-bearing bed of Yanchang Formation was found in recent years in the exploration and development of new Triassic reservoirs in Ordos Basin. Exploration practice has proved that it has good accumulation conditions and favorable exploration potential. With Wubao area in Zhidan County in the central south part of the basin as an example, the authors studied the conditions and distribution regularity of Chang-8 reservoir, and the results show that the Chang-8 oil source mainly came from the overlying Chang-73 source rocks, Chang-8 internal hydrocarbon source rocks and Chnag-9 top hydrocarbon source rocks, thus having a good oil-generating and oil-accumulating reservoir configuration. The migration force of main reservoir-producing stage resulted mainly from hydrocarbon generation pressurization and abnormal high pressure, and the injection of oil and gas into Chang-8 tight reservoir was mainly caused by nearly vertical and lateral migration. Diagenesis exacerbated the reservoir heterogeneity and resulted in the formation of diagenetic occlusion type and quasi-continuous type oil gas accumulations. Chang-8 reservoir plane and horizontal distribution are mainly controlled by the effective hydrocarbon source rocks, reservoir quality and the effective cover layer, and hence various geological factors have resulted in the present Chang-8 reservoir distribution pattern.

    • The sedimentation evolution and favorable sand body distribution prognosis in Chagan sag of Bayin gobi Formation

      2013, 40(4):1169-1179.

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      Abstract:Abstract:The Chagan sag is one of the important bases of strategic energy in the Zhongyuan Oilfield, and the Bayin gobi Formation is the main thin oil exploration strata. Bayi section is the initial rift period of the lake basin, whereas Baer section is the deepening and broadening period of the lake basin. According to an analysis of the data of core observation, well logging and mud logging in the study area in combination with the study of fracture structure characteristics within the lake basin and palaeogeomorphologic signal recovery, the authors have concluded that the palaeogeomorphology of Bayi section is characterized by alternate depressions and slopes, with the development of fan delta, near-shore subaqueous fan, littoral and shallow lake - half deep lacustrine deposition. The palaeogeomorphology of Baer section was influenced by the synsedimentary and deposit faults, showed "two low-lying and two long clip slots" assuming an overall trend of "shallow in the north and deep in the south”, and mainly developed fan delta, frontal fluxoturbidite facies and shore-shallow lake as well as semi-deep lake - deep lake. There are two chief kinds of fracture structure types: plate form and shovel type. The slump turbidite caused by the current active fault is thin and widely distributed, and is the most advantageous area of exploration. The shovel type glutenite is dominated by the secondary fracture, the monolayer is very thick, and fan-delta and coastal submerged fan are well developed, thus becoming the secondary advantageous area. The shovel type glutenite with a narrow distribution and thick monolayer and sediments, with the development of the rapidly deposited coastal submerged fan, is the worst oil reservoir stratum

    • Re-discussion on the geological age of “Nanhao Formation” in Nanhao area, Hainan Island——with comments on the paper “Geological characters and age of Nanhao Formation, Nanhao area, Hainan Province”

      2013, 40(4):1180-1188.

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      Abstract:Abstract:Fairly abundant fossils, such as brachiopods Xinanospirifer flabellum Rong, X. cf. sanduensis (Jing), the trilobite Latiproetus latilimbatus (Grabau), and the gastropod Homotoma sp., were found in the “Nanhao Formation” of Nanhao area, Baoting County, Hainan Island. This fauna strongly supports the conclusion that the fossil-bearing rocks are Late Telychian (Llandovery, Silurian) in age; previously, the rocks were thought to belong to the Aikuanian Stage which is Early Carboniferous in age. Years’ intensive study of the brachiopods from the “Nanhao Formation” of the study area shows that the fossil-lists of brachiopods, comprising Eochoristites sp., Fusella sp., Cyrtiopsis sp., Cyrtospirifer sp., Tenticospirifer cf. supervilis Tien, and T. sp., which have been used as the major evidence indicating an Early Carboniferous age for the “Nanhao Formation” in Nanhao area, are the results of misidentification. Hence, those fossil-lists can no longer be treated as evidence for the stratigraphic subdivision and correlation of the “Nanhao Formation” in the study area. Unfortunately, Chen Zhe-pei and others (2012) concluded incorrectly that the “Nanhao Formation” was Early Carboniferous Aikuanian in age. In the paper “Geological characters and age of Nanhao Formation, Nanhao area, Hainan Province”, they based their conclusions on those fossil-lists. Great efforts were made by the authors in Nanhao area, but no Early Carboniferous brachiopod taxa reported previously were collected again from the original localities. In contrast, a large number of Early Silurian Xinanospirifer were collected from those localities. The above-mentioned data indicate that there are no Lower Carboniferous rocks in the area, and that there is no unconformity between the so-called Lower Carboniferous “Nanhao Formation” and the Lower Silurian Zusailing Formation in Nanhao area, southern Hainan Island. In addition, the Nanbing-Nanhao road-cut section has very complex structures with many faults and folds, strong repetition of beds, disordered sequence, and confusing overlapping relationship of rocks as well as rock thickness. Hence, the road-cut section cannot be treated as the lectostratotype section of the “Nanhao Formation” as previously thought. In summary, both the “Nanhao Formation” as a lithostratigraphic term and the lectostratotype section of the “Nanhao Formation” have to be abandoned.

    • implications from zircon U-Pb ages and Hf isotopic constraint on ore-forming granites in Youmaling and Jiepai deposits

      2013, 40(4):1189-1201.

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      Abstract:Abstract:Youmaling and Jiepai are two newly-discovered tungsten-tin polymetallic deposits with middle-scale metal resources. Their main ore bodies occur in skarn and fractured rocks adjacent to the fine to medium grained monzogranite contacts. In this paper, in situ LA-MC-ICP-MS technology was employed to measure the U-Th-Pb and Hf isotopes of these granites from inner contacts of the Youmaling and Jiepai deposits. Zircon U-Pb isotopic results show that the granites were formed at Ca. 220±1 Ma (MSWD=0.035) and 215±1 Ma (MSWD=0.055) respetively, indicating that Indosinian metallogentic activity took place in Yuechengling-Miaoershan area. εHf(t) values of granite from Youmaling vary between -2.47 and -6.67, and those from Jiepai vary between -3.52 and -6.79, suggesting that they were both remelted from crust rocks. In contrast to other tungsten mineralized granites in the Nanling Mountains, the sources of two granites have higher εHf(t) values. A appropriate reason is that some Neoproterozoic island arc materials with positive εHf(t) values were involved during the remelting of the source materials. Isotopic ages from this paper and previous work indicate that intense Indosinian petrogenetic and metallogentic activities took place in this area. As we all know, fruitful exploration achievements have been obtained in the vicinity of contacts of Indosinian granites in the Nanling Mountains, so more attention must be paid to the exploration and evaluation in this area in the next few years.

    • Metallogenic epoch of the Sandaowanzi gold deposit in Heilongjiang Province: Constraints from the evidence of isotopic age

      2013, 40(4):1202-1208.

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      Abstract:Abstract:Daxinganling area is an essential metallogenic concentration area in Northeast China. In recent years, the Sandaowanzi gold ore deposit was discovered in this area, and gold exists as telluride. In some local places, the grade of gold has reached several percentage points. The study of isotopic chronology of allgovite which crosscuts the quartz-vein shows that the 40Ar/39Ar age of anorhtose is between 115±1.1 Ma and 118±1.2 Ma, which indicates the emplacement age of allgovite. Two volcanic eruption centers of Guanghua period were discovered in the ore district, characterized by strong silicification and pyritization. They have the same age of alteration as the Sandaowanzi gold ore district, which suggests that the gold mineralization took place identical with or later than volcanic eruption of Guanghua period. Zircon age from rhyolite formation of gold is 125.3Ma. Therefore, the formation of the gold deposit should be younger than volcanic eruption of Guanghua period and before the emplacement of allgovite, and hence the metallogenic epoch should be between 125.3Ma and 115Ma.

    • Geological features and Re-Os isotopic dating of the Lalingzaohuo molybdenum polymetallic deposit in East Kunlun

      2013, 40(4):1209-1217.

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      Abstract:Abstract:The Lalingzaohuo molybdenum polymetallic deposit in the Qimantag metallogenic belt of Qinghai Province is a newly discovered skarn –porphyry type deposit. Eleven samples and four repetition samples for Re-Os isotopic dating were analyzed, and the model ages show two segments: 214.1~223.9 Ma and 235.7~240.8 Ma with 187Re-187Os isochron ages of ( 214.5±4.9 ) Ma and (240.8±4.0) Ma and the weighted average model ages of (217.6±3.5) Ma and ( 238.4±1.2 ) Ma , respectively. The age dating indicates that there are two metallogenic epochs: Middle Triassic and Late Triassic. The rhenium content of the molybdenite ranges from 17.40×10-6 to 149.52×10-6, with the great majority concentrated in a dozen micrograms to tens of micrograms, indicating a crust-mantle mixed mineral source. Combined with previous studies, the authors hold that the two ore-forming events in Triassic were associated with the breakoff of the subducting slab in Middle Triassic and lithospheric delamination in Late Triassic.

    • Metallogenic characteristics and ore-forming material sources of the Huachanggou gold deposit in Shaanxi Province

      2013, 40(4):1218-1230.

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      Abstract:Abstract:Located in Lueyang County of Shaanxi Province, the Huachanggou gold deposit is a small-sized deposit which is currently being mined. The gold deposit occurs in the slightly metamorphosed Middle and Lower Devonian strata composed of mafic volcanic rocks (spilite) and marine carbonate rocks. Gold mineralization is strictly controlled by a fault zone. There are mainly three types of ores: altered spilite gold ore, limestone-quartz gold ore and quartz sandstone gold ore. These three types of ores occur respectively in the main ore belt, the north ore belt and the south ore belt, and the south-south ore belt. The S, C, Pb, H and O isotopic compositions show that there is a distinctive difference between the spilite ore and the limestone ore: the ore-forming material source of the former ore came from deep source while that of the latter ore was derived from the upper crust. The Q-type cluster analysis of the trace elements and the REE distribution patterns show that the spilite ore and the limestone ore were closely related to the wall rocks. The geochemical characteristics clearly show that the ore-forming material sources came from the mafic volcanic rocks and the marine carbonate rocks. The data obtained also suggest that the ore-forming fluid was derived predominantly from an active meteoric groundwater system with the addition of small amounts of volcanic water.

    • Fluid inclusions and stable isotope characteristics of the Chalukou porphyry Mo deposit in Heilongjiang Province

      2013, 40(4):1231-1251.

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      Abstract:Abstract:The superlarge Chalukou porphyry Mo deposit, located in northern Da Hinggan Mountains, is the biggest Mo deposit in Northeast China. Its ore bodies are mainly hosted in the intermediate-acid complex and Jurassic volcanic sedimentary rocks, of which granite porphyry, quartz porphyry and fine grained granite are closely associated with Mo mineralization. Three types of fluid inclusions are distinguished based on petrographic and microthemometric criteria, namely liquid-rich two-phase, gas-rich two-phase and daughter mineral-bearing multiphase fluid inclusions. Fluid inclusions in quartz phenocrysts of granite porphyry are mainly liquid-rich two-phase, gas-rich two-phase and daughter mineral-bearing multiphase fluid inclusions, their homogenization temperatures vary from 230 to 440℃ and from 470 to 510℃, and salinities vary from 0.7% to 53.7% NaCl eqv and from 6.2% to 61.3% NaCl eqv, respectively. Fluid inclusions of the ore-forming early stage K-feldspar-quartz-magnetite vein are mainly composed of liquid-rich two-phase, gas-rich two-phase and daughter mineral-bearing multiphase fluid inclusions, and their homogenization temperatures and salinities vary from 320°C to 440°C and from 4.2% to 52.3% NaCl eqv, respectively. Fluid inclusions of the ore-forming middle stage quartz-molybdenite vein and breccia are mainly composed of liquid-rich two-phase, gas-rich two-phase and daughter mineral-bearing multiphase fluid inclusions, and their homogenization temperatures and salinities vary from 260°C to 410°C and from 0.4% to 52.3% NaCl eqv, respectively. Fluid inclusions of the ore-forming late stage quartz-fluorite-galena-sphalerite vein are mainly liquid-rich two-phase fluid inclusions, and their homogenization temperatures and salinities vary from 170°C to 320°C and from 0.5% to 11.1% NaCl eqv, respectively. The ore-forming fluid of the Chalukou deposit is characterized by high temperature, high salinity and high oxygen fugacity, roughly belonging to the H2O-NaCl±CO2 system enriched in F. The δ18OW values of the ore-forming fluid vary from -4.5‰ to 3.2‰, and δDW values vary from -138‰ to -122‰, indicating that the ore-forming fluid was derived mainly from magmatic fluid mixed with meteoric water. The δ34S values of metallic sulfides range from -1.9‰ to +3.6‰, with an average of +1.6‰, suggesting that the ore-forming materials came mainly from deep magma. The multi-stage boiling action of the ore-forming fluid seems to have been the dominant factor for metallic sulfide deposition.

    • Geological-geochemical features and genesis of the Gaoliangdian Fe-Cu deposit in Henan Province

      2013, 40(4):1252-1269.

      Abstract (2969) HTML (0) PDF 5.30 M (4116) Comment (0) Favorites

      Abstract:Abstract:The Louziwan iron-copper deposit is located in the east of East Qinling-Dabie orogenic high-pressure metamorphic belt. It occurs in the Er’langping Group composed of volcanic rocks and sedimentary rocks. The ore bodies with clear layer control features are almost in the lentoid form in the second block of Er’langping Group. Skarnization and silicification are the most important wall rock alterations. It is held that the mineralization has the close relationship with the Er’langping Group, as evidenced by the ore geology, geochemistry, mineral assemblages, sulfur isotope and composition of fluids in minerals. In the early stage, large amounts of basaltic lavas rich in iron and copper were formed in the submarine volcanic activities, thus producing a sedex iron ore layer and carbonate rock during the intermittent period of the volcanic eruption; in the late period, due to regional metamorphism, the basic volcanic rock resulted in the formation of layered skarn, with the superimposition of disseminated, veined copper iron ore mineralization of the hydrothermal origin. It is thus concluded that the deposit belongs to the type of volcanic-sedimentary- metamorphic Fe-Cu deposit.

    • Characteristics of zinc geochemical blocks and assessment of zinc resource potential in western Hunan and eastern Guizhou Province

      2013, 40(4):1270-1277.

      Abstract (2593) HTML (0) PDF 2.02 M (4222) Comment (0) Favorites

      Abstract:Abstract:Based on data obtained from the Regional Geochemistry National Reconnaissance Project (GRNP) of western Hunan and eastern Guizhou and using the theory of geochemical blocks, the authors have studied the characteristics of zinc geochemical blocks and assessed the zinc resources. Four geochemical blocks and seven regional geochemical anomalies were delineated by using 110×10-6 as the threshold of the zinc geochemical block. Statistics and calculation of these four geochemical blocks and other seven regional geochemical anomalies by using the mineral coefficient of 0.36% show that the total predicted mineral resource of zinc is 30.85 million tons (given 1000 m thickness for every rock mass) in western Hunan and eastern Guizhou. It is considered that the four Zn geochemical blocks in Huayuan-Tongren-Zhengyuan, Duyun-Kaili, Dongjiahe and Sanjiaotang areas will be the most important potential areas in further exploration.

    • A prospective analysis of magmatic Ni-Cu sulfide deposits in Huangshan-Jing'erquan area, Xinjiang

      2013, 40(4):1278-1289.

      Abstract (2557) HTML (0) PDF 7.82 M (4251) Comment (0) Favorites

      Abstract:Abstract:In order to improve the application effect of metallogenic regularity in prospecting analysis and mineral prospecting, the authors adopted three steps for exploration work in Huangshan-Jing’erquan area of Xinjiang, The three steps are as follows: (1) the detailed summarization of critical mineral process; (2) the determination of geological factors; (3) the extraction of geological factors from geological, geophysical, geochemical and remote sensing data. These steps help to convert the metallogenic regularity into geological factors by linking the genesis and distribution of ore deposits in space and time to regional geology, geophysics, geochemistry and remote sensing. 13 prospective areas such as Huangshan and Tula’ergen were delineated by using characteristic analysis to study geological factors. The results obtained by the authors indicate the direction for future Ni exploration.

    • The application of integrated geophysical methods to aeromagnetic anomaly inspection of Huidong area

      2013, 40(4):1290-1297.

      Abstract (2750) HTML (0) PDF 4.70 M (4513) Comment (0) Favorites

      Abstract:Abstract:According to the characteristics of the aeromagnetic anomaly in Huidong area, the authors have reached the conclusion that the aeromagnetic anomalies are caused by magnetic bodies in the depth. The integrated geophysical methods, which included ground precision-magnetic survey and audio magnetotelluric sounding (AMT), were used to inspect the aeromagnetic anomaly. Through combining the advantages of different geophysical methods, the authors improved the reliability of the geophysical interpretation. Using integrated interpretation of the data from gravity, magnetic survey and AMT, the authors initially identified the distribution characteristics of the anomaly body in the depth. The integrated geophysical results provide an ore-prospecting clue for the further exploration in this area.

    • The assessment of the intensity of Emeishan basalt weathering based on rock blocks(Ⅱ):hydrogeochemistry of the groundwater in the basalt slope and basalt soaking solution

      2013, 40(4):1298-1306.

      Abstract (2893) HTML (0) PDF 4.69 M (4427) Comment (0) Favorites

      Abstract:Abstract:The evaluation of the element mobility in the process of rock weathering should consider not only elements fixation and leaching status and their concentrations in the leachate (groundwater and laboratory soaking solutions, etc.), but also their relative content in the parent rocks. The ratios of atomic numbers of different elements in the groundwater in Emeishan basalt slope and laboratory soak solution are different from those in basalt parent rocks. The rock-forming mineral dissolution of Emeishan basalt is incongruent. According to the basalt composition change in the course of weathering and the chemical compositions of the groundwater in the basalt slope and the laboratory basalt soaking solutions,the element mobility sequence in Emeishan basalt weathering process of Ca> Na> Mg ≥ Si> K> Fe was determined. Mobile elements sensitive to the degree of weathering or immobile elements should be selected as indicative elements of the rock weathering degree, and Ca, Fe should be the preferred elements to evaluate the weathering intensity of the Emeishan basalt.

    • Identification and significance of the Paleocene-Eocene residual-slope sediments in western Qaidam Basin

      2013, 40(4):1307-1313.

      Abstract (2420) HTML (0) PDF 3.70 M (4256) Comment (0) Favorites

      Abstract:Abstract:The Cenozoic Qaidam Basin has complex sedimentary characteristics, rapid transition of sedimentary facies and various types of lithology. The authors made a systematic analysis of the lithologic characteristics of the overlying strata of the bedrock in the North Kunlun step-fault zone from geological background, core characteristics and microscopic characteristics, and concluded that the sediments are residual-slope sediments. The new understanding of the residual-slope sediments has added a new type of oil and gas reservoirs for oil and gas exploration in the Qaidam Basin and pointed out a new direction for oil and gas exploration of the overlying strata in the bedrock of Qaidam Basin.

    • The data quality control and technique of the mineral resources potential evaluation in China

      2013, 40(4):1314-1328.

      Abstract (10914) HTML (0) PDF 1.34 M (11034) Comment (0) Favorites

      Abstract:Abstract:Exemplified by data quality control of China's mineral resources potential evaluation special project,this paper put forward the data quality control process for the very complex problem domain,systematically illuminated the essential models,methods and techniques of the data quality control,and briefly described the design idea and implementation of the data quality control software system as well as the related research achievements. Practices have verified the effectiveness,feasibility,practicability and representativeness of the data quality control models,methods and techniques,and the results obtained have certain reference significance and application value. The methods and techniques have a very good demonstration effect and application prospect, are suitable for the work of data quality control of various geological spatial data ptoject.

Editor in chief:HAO Ziguo

Inauguration:1953

International standard number:ISSN 1000-3657

Unified domestic issue:CN 11-1167/P

Domestic postal code:2-112

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