Abstract:Abstract：The Sino-Mongolia border region and its neighboring areas are located at the convergence zone of the Siberian platform, Tarim plate and North China craton, and is one of the most important uranium metallogenic provinces in the world. Deep-seated faults, pre-Jurassic metamorphic terrane and various types of uranium deposits (mineralized areas) are well developed in the region due to the multiphase tectonic-magmatic events. These uranium deposits can be classified into six types in term of their host rocks, geometry and ore-forming processes: (1) volcanic type; (2) sandstone type; (3) vein type; (4) lignite type; (5) metasomatitic type; (6) phosphorite type, among which the first two types of uranium deposits bear the most important economic significance. Regional metallogenic studies show that most of the uranium deposits (or mineralized areas) occurring within the Sino-Mongolian border region are closely spatially associated with pre-Jurassic metamorphic terrane consisting of two parts: (1) Precambrian high-grade metamorphic rocks; (2) Paleozoic lightly metamorphic rocks. Since uranium is a lithophile element, it is more easily enriched in the acidic sialic section of the crust during the differentiation of mantle matter. Because these old formations had already been enriched in uranium through the long geological evolution, they might have provided the precondition for economic enrichment of uranium in the Phanerozoic tectonic movements when downfaulted or downwarped continental basins occurred with terrestrial dominated sediments. Where the uranium-enriched geological bodies existing in one region are eroded, all of them can serve as the source for the sandstone-type deposits. The early tectonic event occurring around 176 to 125Ma provided suitable conditions for the oxidization of the groundwater table and the formation of low-grade uranium mineralization area. In the Phanerozoic tectonic-activated regions, the economic enrichment of uranium usually occurred in intensive rejuvenated places of the pre-Jurassic metamorphic terrane. The gradual enrichment of uranium in the sialic crust is mainly achieved through two differential processes: granitization and sedimentary differentiation. However, this combined process is very slow and takes a long time. The ore-forming processes of volcanic type uranium deposits may be an integrated part of the uranium-bearing granitization. For the volcanic type uranium deposits occurring in the easternmost segment of the Sino-Mongolian border, they were formed during the time of tectonic extension when a number of troughs that were filled with high K-felsic vocanics were formed within the Central Mongol-Argun terrain. Several large-sized Pb-Zn-Ag-U deposits have been identified in the felsic volcanic complexes. Both uranium and fractionated peralkaline magma were produced by the intensive rejuvenation of the pre-Jurassic metamorphic terrane. The formation processes of the sandstone type uranium deposits might have been genetically related to Late Jurassic to Early Cretaceous igneous activities. Geochronological studies (U-Pb isotopes on uranium ores) demonstrate that the uranium ores formed around 153 to 136 Ma. That time of the uranium ore formation coincides with the formation age of andesitic basalt and rhyolite of the Dornod Formation. Late Jurassic to Early Cretaceous ages are practically equivalent to the formation time of uranium deposits in the Streltsosk caldera in Russia (136-134 Ma). The high K rhyolite is clearly enriched in uranium (about 30×10-6), making it the probable uranium source. The high U content of the melt inclusions (U, 14×10?6-25×10?6) from the rhyolite provides the further evidence for the hypothesis mentioned above. The Early formed uranium mineralized zones were intensively overprinted by the hydrothermal events associated with the emplacement of the high K-felsic magma. Widespread pyrite, galena, sphalerite and marcasite suggest formation from metastable sulfur species, which are powerful reductants. Most of the sandstone type uranium deposits occur in the Meso-Cenozoic rift basins filled with various sediments. The uranium-bearing layers formed by amalgamation of braided channels deposited in a fluvial, terrestrial delta and offshore environment. All these sandstone uranium deposits were formed at the last stage of phaneroic tectonic movement when downfaulted or downwarped continental basins occurred with terrestrial dominated sediments. The Early tectonic event (176-156 Ma) provided suitable condition for the paleo-phreatic oxidation and led to the formation of low-grade uranium mineralized zones. During the period of Late Cretaceous (96 Ma) to Oligocene (35 Ma), the uplifting erosion and sedimentation resulted in suitable condition for the inter-layers oxidation and led to the formation of major sandstone type uranium deposits.Geological and geochemical features of both volcanic type uranium deposit and sandstone type uranium deposit have attracted much attention among geologists both in China and abroad. The integrated analyseis of the geological setting, geological and geochemical features of these deposits and their related wall rocks will greatly upgrade the understanding of the ore-forming processes of the uranium deposits. Meanwhile, the genetic model and mineral exploration criteria of these uranium deposits can also be used during the comprehensive evaluation of the concealed uranium deposits in the China-Mongolia border region and its neighboring areas.

Abstract:Abstract: In recent years, many porphyry-type Cu deposits have been found in Mongolian Gobi-Tianshan and in Chinese Beishan and Tianshan. This paper summarizes geological characteristics and metallogenic age data of typical porphyry-type deposits in these areas and suggests that the deposits were mainly formed during Devonian-Carboniferous. Meanwhile, most of these deposits are genetically related to adakites, indicating that they were formed in a volcanic arc setting. It is held that the deposits in these areas likely constitute a single giant porphyry-type metallogenic belt, which straddles the border between China and Mongolia. The features are analogous to features of the porphyry deposits in Neocene, implying great resource potential of CAOB (Central Asian Orogenic Belt).

Abstract:Abstract: SHRIMP U-Pb data of zircons from the strongly greisenized granite at the Khar Morit W-Sn ore deposit in Gobi Tianshan of South Mongolia shows that the emplacement age of granite intrusion is (214±3) Ma, which indicates that the W-Sn mineralization of the deposit took place during Triassic in Early Mesozoic. According to the comprehensive analysis of the data avialable, the authors hold that two episodes of W-Sn mineralization existed in Beishan area of China: one in Devonian and the other in Triassic. The metallogenic time of the Khar Morit W-Sn deposit in Mongolia’s Gobi Tianshan is coeval with that of the second W-Sn ore-forming event in Beishan, China. The spatial-temporal relationships between the tectonic evolution and the W-Sn mineralization suggest that the W-Sn ore deposits produced during the two metallogenic episodes all occurred in a collision to post-collision setting. The Devonian W-Sn ore deposits were related to the collisional event between the Dunhuang and Beishan blocks, which took place during Late Silurian-Early Devonian period, whereas the Triassic ones were likely related to the orogeny brought about by the final closure of the Paleo-Asian Ocean at about the end of Late Paleozoic.

Abstract:Abstract: The Erentaolegai silver deposit is a large epithermal silver deposit in Inner Mongolia. In this paper, chronologic and geochemical research were carried out on such intrusions as quartz porphyry, quartz monzonite, biotite syenogranite and fine-grained granite in the ore district. The zircon LA-ICP-MS U-Pb dating?results show that the zircon U-Pb ages of the four intrusion samples are (285.4±1.9) Ma, (294.3±0.6) Ma, (287.0±1.2) Ma and (243.9±1.6) Ma respectively, which shows that the intrusions in the ore district were formed in the two periods of Late Hercynian and Indosinian. The age of the first three samples show that they were formed by magmatic evolution in the Late Hercynian period, and their geochemical features show the depletion of large ion incompatible elements such as Ba, Nb, Sr, Zr and Ti, the remarkable enrichment of K and the depletion of Ta, with weak negative Eu anomalies, and exhibit arc granite characteristics in (Y+Nb)-Rb and Yb-Ta?tectonic environment discrimination diagrams for granitic rock and peraluminous S type granite, which suggests that they were formed in a tectonic environment of syn-collison in combination with the regional tectonic evolution. The zircon U-Pb age of the fine-grained granite is ( 243.9±1.6 ) Ma, suggesting that it was formed by magmatic evolution in the Indosinian period; in addition, its geochemical features show the depletion of large ion incompatible elements such as Ba, Nb, Sr, Ti, Zr and Ti, the remarkable enrichment of K and the loss of Ta, with weak negative Eu anomalies, and has arc granite characteristics in (Y+Nb)-Rb and Yb-Ta?tectonic environment discrimination diagrams for granitic rock and peraluminous S type granite, which implies that it was formed in a tectonic environment of volcanic arc in conjunction with the regional tectonic evolution. According to previous studies, the wall rock of the ore district is Tamulangou volcanic rock formed in the Middle Jurassic, and its 40Ar-39Ar?isochron age is (162.6±0.7) Ma, which shows that there is no genetic relationship between the intrusion and the deposit.

Abstract:Abstract: The Shuangjingzi complex occurs on the southern and northern sides of the Xar Moron River in Linxi County, eastern Inner Mongolia and is composed of schist, gneiss and gneissic granite. There exists controversy over timing of the Shuangjingzi complex. Some researchers hold that it belongs to Precambrian metamorphic rocks，while others argue that it belongs to the Early Mesozoic strong structural deformation products. In this paper, the authors studied zircon geochronology of the main rocks in the Shuangjingzi complex by using the LA-MC-ICP-MS method with the purpose of constraining the timing of the complex. The zircon dating results show that the 206Pb/238U ages of the chlorite schist range from 146.3 Ma to 1970 Ma, with no reliable weighted mean ages obtained due to the too scattered ages. The 206Pb/238U ages of the biotite plagioclase gneiss vary from 146.3 Ma to 1736 Ma, with two reliable weighted mean 206Pb/238U ages of （290.5±2.1） Ma (MSWD = 0.36, n=10) and （247.5±3.4） Ma (MSWD = 2.9, n=5), respectively, indicating that two epochs of magmatic emplacement events took place in the original rocks of the complex during Early Permian and Early Triassic, respectively. The zircons from the granite pegmatite that intruded into the complex do not give a reliable weighted mean age, with the scattered 206Pb/238U ages ranging from 206.9 Ma to 2122 Ma, while the zircons from the gneissic granite occurring within the complex yielded a weighted mean 206Pb/238U age of （278.4±1.4） Ma (MSWD=1.9，n=16), suggesting that the emplacement of the original rock occurred during Early Permian. Geochemical analyses show that the Shuangjingzi complex, including chlorite schist, biotite plagioclase gneiss and gneissic biotite granite, is characterized by complicated constituents, with SiO2 content from 61.97% to 77.18%. All samples collected from the complex have the features of LREE differentiation, and are enriched in LILE elements with relative depletion of U, Nb, Sr, P and Ti, and enriched in Th, K, Ce, Nd, Hf, Sm, Y and Yb. A comparison with the Shuangjingzi complex shows that the granite pegmatite exhibits similar enrichment and depletion trends of the trace elements, except for the distinctive relatively depleted Ba and enriched Ta. Therefore, the Shuangjingzi complex is composed of the mixture of rocks (including strata and magmatic rocks) of different compositions and ages,. Based on the age data available and the zircon ages obtained by the authors, it is held that Shuangjingzi complex consisting of a set of low-medium grade metamorphic rocks occurring along the Xar Moron River deep-seated fault was formed between 230 and 206 Ma, resulted from the collision between North China and Siberian Plates, and might have been reworked during Middle-Late Yanshanian period. Therefore, no Precambrian basement exists in the study area.

Abstract:Abstract: The Ullan lead-zinc deposit in Mongolia, together with Tsav, Jiawula, Chaganbulagen lead-zinc deposits, forms a lead-zinc ore concentration area in the Kerulen-Manchuria metallogenic belt. Geological characteristics of the Ullan deposit were described in the aspects of ore-bearing strata, ore-controlling structure, ore-bearing dike, wall rock alteration and orebody characteristics. Rock geochemical studies show that ore-bearing rocks are calc-alkaline volcanic rocks with medium-high Si, medium-Al and high K. The rocks are enriched in large-ion lithophile elements (Ba, Rb, Ce), high field-strength elements (Nb, Ta, Th), Zr and depleted in Li, Sr, Y, with the data ∑REE=412.25×10?6-999.06×10?6,（La/Yb）N=4.41-43.10 and strong Eu anomalies (δEu=0.56-0.88). Zircon LA-ICPMS U-Pb isotope ages indicate that wall rocks formed in Late Jurassic (from （150.8±4.4） Ma to （164.7±3.1） Ma). The authors also determined that Ullan lead-zinc deposit was formed in a rift setting after the formation of Transbaikal-Da Hinggan Mountains?transpressional?arc in the period of 140-155 Ma and hence belongs to the hypabyssal hydrothermal vein-type deposit controlled by explosion breccia.

Abstract:Abstract: Geochronology, petrology and petro-geochemistry of hypersthene-plagioclase granulite from Liangcheng area of central Inner Mongolia were investigated, and its forming age and tectonic background were discussed. The age of hypersthene-plagioclase granulite dated by LA-ICP-MS U-Pb of zircons is (1935±9) Ma, indicating that it was formed in Paleoproterozoic. Research shows that the rock mass was formed in a plate tectonic environment, the study area experienced mantle upwelling accompanied by underplating basaltic magma about 19 billion years ago, and the basaltic magma was intruded into the lower crust and caused the granulite facies metamorphism.

Abstract:Abstrac: The authors collected a large number of data about U-Pb ages of zircons through compling the relative probability plot of detrital zircons, briefly discussed the evolution history of the Siberia craton, North China craton, Northeast China micro-block and Dashizhai area of Inner Mongolia. The comparative analysis of ages for the Permian strata in Dashizhai area of Inner Mongolia and the neighboring old blocks can help to study the problem of the source of Permian strata in Dashizhai area of Inner Mongolia. Based on the ages of detrital zircons from the South Siberia craton, North China craton, Northeast China micro-block and the Permian strata in Dashizai area in comparison with zircon ages of blocks in neighboring areas, the authors discussed the provenance and made research on zircons U-Pb chronology. The source of the Permian strata in Dashizhai area of Inner Mongolia was reasonably determined. The study of the ages of detrital zircons shows that detrital zircon ages of Permian strata in Dashizai area of Inner Mongolia can be divided into the Paleozoic age group (500-250 Ma), the central and late Proterozoic age group (1.6-0.8 Ga) and the late Archean age group (2.6-1.7 Ga ), whereas on the northern margin of North China craton and on the southern margin of Siberian craton, zircon U-Pb ages are earlier than 1.6Ga. Both of them fail to reflect the reasonable age information of the Permian strata source in Dashizhai area of Inner Mongolia. The age peaks of the Northeast China micro-block in China are consistent with the age peaks of the Permian strata from Dashizai area, which indicates that the provenance of the Permian strata came from the Northeast China block rather than the northern margin of North China craton and the southern margin of Siberian craton. Large quantities of ages of zircons from old basements indicate the existence of ancient micro-continents in Northeast China that may be independent of Siberia craton and North China craton, which is consistent with the view that there existed an ancient micro-continent in the central Asian orogenic belt. Northeast China block might have consisted of many small blocks after collision, and it then collided with the Siberia craton and the North China craton, with the collision taking place respectively along the Hegenshan-Heihe suture zone and Silas Mulun suture zone.

Abstract:Abstract: The Gobi-Tianshan Fault System (GTFS) extending over 700 km long is one of the largest strike-slip faults in the Central Asia Orogenic Belt (CAOB), which was considered to accommodate the eastward extrusion of Tibet. On the basis of tectono-geomorphic interpretation of satellite remote sensing images along GTFS, this study aims to document the Late Cenozoic structural deformation and geomorphic features. Geomorphic features, such as fault scarps, displaced rivers and varied restraining bends, are well developed around the GTFS. Visible fault scarps cutting across Late Cenozoic alluvial sediments, whereas low mountain-front sinuosities and deeply incised narrow canyons in the range front can indicate Late Cenozoic fault activity. The authors identified a ca. 2000 m-long lateral offsets of rivers, which are related to prolonged geomorphic growth of the GTFS. Historical earthquake data are consistent with deforming continental interior region, with tectonic loading shared amongst a network of faults, which indicates a complex earthquake prediction. Meanwhile, three restraining bends were identified in the study area: Karlik Tagh, Gurvan Sayhan and Nemgt Uul, of which the first two restraining bends are located in the two termination zones of the strike-slip fault, whereas the last one occurs in the converging and overlapping position of two separate strike-slip fault segments. Strike-slip fault cutting through the regions of restraining bend mountain ranges might have been an important mountain-building process in the CAOB.

Abstract:Abstract: Xilin Gol complex occurs in Xilinhot-Daqingmuchang area and is composed of metamorphic supracrustal rocks, metamorphic basic-ultrabasic rocks and granitic gneiss, with some of them being Precambrian in age and constituting Precambrian block. Recent dating of the LA-MC-ICPMS U-Pb zircons from parametamorphic rocks of Xilin Gol complex in Huremutaiaobao and Baiyintaolegai area yieled ages of detrital zircons ranging from 403Ma to 3077 Ma with a group of 206Pb/238U ages in the youngest strata between 403 and 420 Ma, probably representing the lower limited age of the sedimentary rock. Combined with 337 Ma metamorphic age of the parametamorphic rocks which were emplaced by arc intrusive rocks of Early Carboniferous-early Late Carboniferous, the authors hold that the parametamorphic rocks were formed in middle Early Devonian-early Early Carboniferous, and their protolith belonged to normal sedimentary rocks without being subjected to volcanic activity, and hence it was not characterized by forearc deposition formation. Therefore, it comprised a set of strata deposited on Precambrian Xilinhot micro-block, representing initial deposition of the southern margin of Late Paleozoic Hegenshan Ocean basin with extension after Early Paleozoic collision orogenesis.

Abstract:Abstract: Lying in the Ergun massif, the Jiageda Formation is a part of the Xing’an orogenic belt. It is composed of pillow lava, schist, mica-schist, marble, marbleized limestone and meta-basalt rocks. The meta-basalt rocks with pillow structure in the Jiageda Formation are Na-rich Na alkaline basalts, with high content of TiO2, P2O5 and Na2O; the rare-earth elements are characterized by right-oblique strong LREE-enrichment patterns and high ∑REE values of 107.71×10-6~127×10-6; the rocks are enriched in such HFSH as Nb, Ta, Zr, Hf as well as such LILE as Rb, Sr, Ba and LREE, with LREE/HREE ratios being 5.15-5.56, (La/Yb)N being 4.44-5.18, and δEu being 0.86~1.08.The trace element patterns are of the upward-bulging K-Ti enrichment type, and their multi-component plots fall within the fields of oceanic island basalts and alkali basalts. These basalts are characterized by the tectonic setting of the oceanic intraplate alkaline basalts. The geochemical characteristics indicate that the meta-basalt rocks belong to the OIB. The discovery of the OIB shows that there once existed well-developed Palaeo-oceanic crust. Judging from the geological and geochemical features of the meta-basalt rocks in the area,the authors conclude that they were derived from the asthenosphere mantle or mantle plume.

Abstract:Abstract: The Central Asian Orogenic Belts (CAOB) resulted from evolution and final closure of the Plaeo-Asian Ocean(s). Located in the central segment of the southern portion of the CAOB, the Beishan area, which refers to the conjunction region of Inner Mongolia, Gansu and Xinjiang, is one of the most important metallogenic belts in China, with abundant Cu, Mo, Au, Fe and base metal deposits. Two collisional events took place in the Beishan area during Late Paleozoic-Early Mesozoic: one occurred at the end of Late Paleozoic, which was related to the final closure of the CAOB, and the other took place in Early Mesozoic, resulting from the closure of the Carboniferous-Permian rifts in southern Beishan. As a consequence, the Beishan area was involved, in terms of temporal relations, in a collision to post-collision stage in Indosinian epoch of Mesozoic period, during which large-scale ductile shear zones and intensive magmatism as well as associated metallic mineralization occurred. The Mesozoic magmatism, which is predominated by intermediate-felsic intrusions locally with minor basic ones, is characterized by plutonic intrusive facies, without extrusive counterpart. Petrogenically, S-, I-and A-type granites have been delineated in the area. Types of Mesozoic mineral deposits in the area mainly include porphyry-type Mo mineralization, which is associated with I-and/or A-type granites, W (Sn) deposits associated with S-type granites, skarn-type Au-Ag-Cu polymetallic deposits associated with intermediate-felsic intrusions, and Au deposits related to granitic intrusions and controlled by ductile shear zones. Indosinian epoch is the latest period of major magmatism and metallic mineralization in the area, to which more attentions should be paid since the Indosinian granitoid intrusions and associated mineral deposits may be much more extensive and abundant than recognized presently.

Abstract:Abstract: The studied glaucophane schist is in the Ordovician Halahahe Formation of Subugeta, Inner Mongolia, and there are a variety of rock assemblage types. According to the optical characteristics and EMP analysis, the authors have come to the conclusion that the glaucophane schist is a kind of ferriglaucophane in the study area. The topomineral assemblage of glaucophane schist is characterized by glaucophane + epidote + actinolite + phengite + sphene. The schist was cemented and recrystallized by shaly clasolite, and the formation environment of native rock was the marginal-sea basin of the continent. The metamorphic origin belonged to the regional low-temperature/middle-high pressure dynamic metamorphism related to plate movement.

Abstract:Abstract: Systematical sampling of major granite rocks in the Badaguan ore district was conducted in this paper. Microscopic identification results reveal that the primary rocks include granite, biotite granite, granitic porphyry, moyite, and granodiorite porphyry, whereas LA-MC-ICP-MS zircon U-Pb ages of the six samples vary in the range of 243.87-231.63 Ma. Combined with emplacement ages of the metallogenic porphyry, it is inferred that all intrusive rocks were developed in the Indo-Chinese period, without existence of Hercynian or Yanshanian intrusions. According to the distribution of the ages, Indosinian magmatic activities were mainly concentrated in 243.87-237.11 Ma and 231.63-229.00 Ma, and surrounding rocks formed at the early stage of magmatic activity. Copper and molybdenum mineralization principally occurred at the late stage of magmatic activity. In addition, Indo-Chinese magmation on both sides of Okhotsk orogenic belt also have the similar two-stage characteristics, which was closely related to subduction of the Okhotsk Ocean. Based on summarizing the situation on both sides of the identified porphyry deposit, the authors consider that there exists possibility in the search for porphyry deposits of the early Indosinian period in the periphery of the Badaguan ore district or/and Ergun area.

Abstract:Abstract: A study of whole-rock Sr-Nd isotopes, Pb isotopes of K-feldspar and Hf isotopic compositions of zircons from the ore-bearing granites in the Honghuaerji scheelite deposit was carried out in this paper. The results show that the average (87Sr/86Sr)i ratios of pink monzogranite, gray monzogranite and quartz monzonite are 0.70525, 0.70517 and 0.70482 respectively, displaying a decreasing trend; however, the average εNd(t) values are +2.2, +2.3 and +3.1 respectively, exhibiting an increasing trend. The Pb isotopic compositions of K-feldspar samples selected from pink and gray monzogranites are relatively uniform, with the 206Pb/204Pb ratios ranging from 18.258 to 18.276, 207Pb/204Pb ranging from 15.507 to 15.512 and 208Pb/204Pb ranging from 37.994 to 38.018. The εHf(t) values of zircons from the three samples are +5.2?+10.4, +3.1?+9.8, +5.8?+14.4 respectively. The Sr-Nd-Pb-Hf isotopic compositions show that the granites-forming materials might have been derived from a depleted mantle during Neoproterozoic. The quartz monzonite was likely the inclusion which was a product of magma mingling. The regional tectonic analysis indicates that the magma resources were probably related to the interaction between the ocean plate and the upper mantle during the closure of Paleo-Asian Ocean before Mesozoic Era; and after the disappearance of Mongolia?Okhotsk marine trough, the compression tectonic setting that had resulted from the collision of plates triggered the partial melting of the resources in early Jurassic epoch.

Abstract:Abstract: Located in the northwest of Hailar-Genhe Mesozoic volcanic basin, the Biliyagu lead-zinc-silver deposit occurs in the Upper Jurassic Manketouebo Formation acidic volcanic rocks and is controlled by the NW-trending faults, with the orebodies being mainly of vein type. LA-ICP-MS zircon U-Pb dating of rhyolitic volcanic breccia lava indicates that its age is (159.2±1.8) Ma. Based on the relationship between the rock and the mineralization, the authors hold that the deposit was formed in late Jurassic. Major element geochemistry of rhyolitic volcanic breccia lava and rhyolite is characterized by high SiO2 (68.31%-77.18%), potassium (3.39%-4.28%), and aluminum (11.74%-14.93%) and low sodium (0.14%-0.18%), suggesting high potassium calc-alkaline series. The REE content of rocks is low (93.65×10?6-98.94×10?6), and has characteristics of high LREE and LREE/HREE ratios as well as weak Ce negative anomaly and Eu negative anomaly. Combined with the features of the rocks such as the loss of the Sr and the obvious enrichment of LREE, it is inferred that the volcanic rocks originated from the plate. The magma of rocks might have been derived from the upper mantle and mixed with crustal materials. Combining this study with regional tectonic evolution characteristics, the authors hold that the deposit was formed during the closure period of Okhotsk plate in a tensile extension environment.

Abstract:Abstract: Located in the middle of Derbugan metallogenic belt in Inner Mongolia, the Badaguan copper-molybdenum deposit is a typical porphyry deposit with obvious phyllic and propylitic alteration zones. The banded orebodies occur in Triassic quartz diorite. By such means as Re-Os isotope geochronology, element geochemistry and sulfur isotope geochemistry, the authors preliminarily analyzed the ore-forming process of the deposit. Re-Os dating of molybdenite gave a weighted average model age of (226.7±2.4) Ma, implying that the deposit was formed in the early Late Triassic. Element geochemical analysis shows that the ore-bearing rocks were I-type granites and belonged to calc-alkaline rock series with moderate content of potassium, which were produced in a volcanic arc environment with characteristic active plate edges. During the ore-forming process, ΣREE in ore-bearing rock gradually decreased, and the ratio of LREE to HREE became higher. The δ34S values of metallic sulfides range from +0.5‰ to+4.8‰, suggesting mantle sulfur origin. Based on a comprehensive analysis, the authors hold that the Badaguan copper-molybdenum deposit was formed in the Late Triassic. During the southward subduction of Mongolia-Okhotsk Ocean plate, magmatic activity at the depth brought lots of ore-forming materials, and partially melted oceanic plate was emplaced above Ergun block. Cu, Mo and other elements migrated with the hydrothermal fluids and combined with sulfur from the mantle, eventually resulting in enrichment and mineralization.

Abstract:Abstract: The Wunugetushan porphyry Cu-Mo deposit is one of the typical deposits in the Deerbugan metallogenic belt. Combining laboratory analysis with field observations, the authors quantified the migration of ore-forming elements by immobile plateau method and the formula given by Grant, and discussed the metallogenic processes. The results show that the percentages of SiO2, Al2O3, MgO, Fe2O3 gradual increased from the inner part to the outer part due to the continuous decrease of temperature, the migration of major elements led to the formation of some minerals whose zoning is consistent with the zoning of characteristic minerals such as quartz, feldspar, sericite and muscovite in Wunugetushan alteration zone. The magma originated from the mantle and was contaminated by crustal materials during the collision between Siberia plate and Mongolia plate. Cu, Mo were brought into the alteration zone, the percentage of the gaining (Xgp) of Cu and Mo was gradually reduced from the inner part to the outer part. Mo came from the surrounding rocks, whereas Cu was from parent rocks. In the course of alteration of plagioclase Mo precipitated and entered hydrothermal solution due to the complexation of CO32? , and then migrated. Pb and Zn were taken out of the inner zone and brought into the outer zone, and the elements were eventually concentrated in the outermost zone.

Abstract:Abstract: Located in the southern part of the Da Hinggan Mountains metallogenic belt, the Bianjiadayuan silver polymetallic deposit is a typical hydrothermal vein-type deposit. Stable (C, H, O and S) and radiogenic (Pb) isotopes of the Bianjiadayuan silver poly-metallic deposit were analyzed with the purpose of determining the source of the ore-forming fluids and materials. TheδDH2O-SMOW and δ18ОH2O-SMOW of the ore-forming fluids are -138.5‰- -111.7‰, and -8.85‰ -9.38‰, respectively, showing that they came from the mixing of magmatic water and meteoric water. The δ13CPDB and 18OSMOW of the hydrothermal calcite vary from -7.7‰ to -2.67‰ and from-0.41‰ to 6.03‰, respectively, indicating that the hydrothermal calcite was formed at two ore-forming stages. At the early stage, the ore-forming fluids were similar to magmatic water and the CO2 was related to the magma, whereas at the late stage, the ore-forming fluid was derived from meteoric water. The δ34S values of polymetallic ore in the Bianjiadayuan deposit range from 0.7‰ to 4.4‰, suggesting that the formation of the Ag-Pb-Zn orebody was closely related to magmatism and the sulfur probably came from the magma source. The ratios of lead isotopes in sulfides range from 38.1 to 38.634 for 208Pb/204Pb, 15.518 to15.681 for 207Pb/204Pb, and 18.155 to 18.284 for 206Pb/204Pb, respectively, indicating that the mineralization might have been induced by the magmatism, and the lead in the deposit was mainly derived from deep-seated magmatic source. The mineralization took place in a low δ34S∑S and equilibrium system. The Bianjiadayuan deposit can be genetically regarded as a volcanic-subvolcanic hydrothermal vein-type silver polymetallic deposit.

Abstract:Abstract: Since the localization of the most of the uranium geological prospecting units in 2000, The geological party of CNM carried out geological exploration projects and surveys in Ordos, Erlian and Bayingobi Mesozoic-Cenozoic sedimentary basins in consistency with the strategic plan of “in situ leaching sandstone uranium as the predominant uranium type in north China”. A breakthrough in prospecting was achieved, and all achievements have also been constantly expanded in the subsequent exploration. In addition, both Ordos Basin and Erlian Basin were listed as the first batch of equipped exploration areas in 2011. As expanding and consolidating existing achievements in the same time and summarizing the key factors and patterns of prospecting breakthrough constitute particularly important steps for the achievement expanding and discovering of new deposits. Based on the basic characteristics of main Mesozoic-Cenozoic sedimentary uranium basins of Inner Mongolia, this paper sums up crucial techniques and methods for prospecting breakthroughs, analyzes uranium ore-forming potential and exploration prospect, and points out the three metallogenic belts of Husiliang, Bayinggebi-Saihantala-Qiha, and Yingejing edge as the key areas to expand the achievement.

Abstract:Abstract: Based on detailed analysis of regional metallogenic geological background and conditions, it is held that the Duolong ore district of the West Bangong Lake arc has metallogenic prospecting and resources potential for porphyry Cu-Au deposits. Through the exploration in 2013, the authors made a breakthrough in Tiegelongnan. Copper reserves of the Tiegelongnan ore district has reached a superlarge ore deposit, and this deposit has thus become the largest porphyry Cu（Au） ore deposit in the Duolong ore district as well as the major exploration breakthrough in 2013. The deposit is located in early Cretaceous Meiriqiecuo formation of the middle Duolong ore district, and has a close temporal relationship with early Cretaceous intrusive granodiorite porphyry, granite porphyry and concomitant hydrothermal mineralization breccia. The orebodies mainly occur in the lower middle Jurassic Sewa Formation feldspar quartz sandstone, lithic sandstone intercalated with dark gray to deep black silty slate and mineralized porphyry. Orebodies exhibit concealed dome and are characterized by great downward extension in the forms of network veins, veinlets, and disseminations. Hydrothermal alteration is well developed, with obvious zonation, strong silicification, sericitization, and widely superimposed advanced argillic alteration. The denudation degree of the ore district is very low. The surface only develops limonite and clay, with no copper mineralization. Alteration and mineralization increased gradually downward, and the mineralization extension reaches one thousand kilometers at depth without closure. The upper copper mineralization is of chalcocite-digenite-enargite association, exhibiting characteristics of the Cu-S system, which gradually changes into bornite and chalcopyrite characteristics of the Cu-Fe-S system. Copper mineralization is associated with Au, Ag mineralization and assumes positive correlation. Compared with other porphyry Cu-Au ore deposits in the Duolong ore district, this deposits is poor in gold. The exploration breakthrough of the deposit provides a good example for the exploration work of the mining company and also has significance for regional ore-prospecting.

Abstract:Abstract: In this paper Mingnandong pluton was studied throughly by such means as field observation, LA-ICP-MS zircon U-Pb isotopic measurement and petro-geochemistry. The results show that Mingnandong pluton was formed in the Early Jurassic (180.47±0.71Ma). Chemical analyses yielded the following data for Mingnandong pluton: SiO2=60.71%-67.72%, Al2O3=15.60%-17.44%, Na2O+K2O=6.79%-7.63%, K2O/Na2O=0.61-1.01 and A/CNK=0.94-1.01, implying high-potassium calc-alkaline I-type granites. Besides, Mingnandong pluton is enriched in light rare earth elements and large ion lithophile elements, and depleted in heavy rare earth elements and high field strength elements. These features suggest that Mingnandong pluton has obvious characteristics of active continental margin and volcanic arc granites. The ingredient zonation parallel to the orientation of the subduction of oceanic crust made up of cale-alkaine, high-K calc-alkaline granites and the bimodal volcanic rock association from Yanbian and Taiping Mountain to Xiao Hinggan Mountains and Zhangguangcai Mountain indicate the orientation of the subduction of ancient Pacific plate. In a word, the emplacement of Mingnandong pluton was influenced by the subduction of ancient Pacific plate in the Early Jurassic.

Abstract:Abstract: The Bikou Group basalt lenticular or banded in form is distributed in tuffs and tuffaceous phyllites of Huachanggou area. Based on detailed field geological survey and systematic laboratory studies including microscope observation, major and trace element analysis and radioactive isotope analysis, the authors investigated the petrological, geochemical and chronological characteristics of the basalt. The result shows that the basalt in Bikou Group has been subjected to metamorphism of greenschist facies, and mainly consists of plagioclase, chlorite and epidote. The basalt exhibits low SiO2 (44.67%-49.76%), TiO2 (1.14%-1.34%) and REE, high TFe2O3 (12.03%-15.47%), MgO (7.57%-9.3%) and CaO (7.29%-10.54%), with LREE depletion and HREE enrichment. It originated from asthenosphere, occurred in N-MORB setting and was mixed with the old crust. The basalt sample yielded zircon LA-ICP-MS U-Pb age of (316.3±6.0) Ma (MSWD=0.78; n=7), which indicates that the Bikou Group volcanic rocks are products of at least two periods of volcanic activities, i.e., Neoproterozoic and late Paleozoic. They were formed massively in Neoproterozoic and reformed by the volcanic activity in late Paleozoic.

Abstract:Abstract: This paper reports retrograde eclogite that occurs in lanticular form in Xikou area of Jiangshan-Shaoxing suture zone. The retrograde eclogite consists of the mineral assemblage of amphibole+garnet+clinopyroxene+plagioclase+quartz. A clear ‘white-eye' structure is well developed, garnet is rimmed with symplectitic plagioclase, and clinopyroxene is surrounded by symplektic plagioclase and amphibole. Zircon U-Pb dating by LA-ICP-MS shows that the peak metamorphic age is （451+8/-18）Ma. Exposures of retrograde eclogites in the Jiangshan—Shaoxing suture zone provide new insight for the collisional process between the Cathaysia block and the Yangtze block.

Abstract:Abstract: The Dashimengou molybdenum deposit in Songxian County of Henan Province is a newly discovered large molybdenum deposit in western Henan. Five samples of molybdenite-bearing breccia and there samples of molybdenite-bearing broken quartz related to mineralization were selected for precise molybdenite Re-Os dating, and the model ages obtained are from (156.1±3.4) Ma to (228.0±4.1) Ma. The model ages can be obviously divided into two groups: the Re-Os model ages of the first group range from (208.4±3.1) Ma to (228.0±4.1) Ma, with an average model age of (218.07±4.3) Ma and a weighted average model age of (217.1±8.5) Ma; the second group range from (156.1±3.4) Ma to (160.9±3.3) Ma, with an average model age of (158.6±3.35) Ma and a weighted average model age of (158.6±4.7) Ma. The results show that the Dashimengou molybdenum deposit was formed in the Indosinian and Late Yanshanian periods. The ore-forming processes of the two phases were related to two cryptoexplosion events of the hydrothermal breccia. The rock-forming and ore-forming activity of Indosinian period occurred in the transition period of the tectonic regime from compression to extension after collision orogenic movement of the East Qinling molybdenum ore belt. The upwelling of partially melted upper mantle and lower crust produced cryptoexplosion at the intersections of NW-and NE-trending structures. Late Yanshanian mineralization seems to have been the inheritance, transformation and superposition of the Indosinian mineralization, and the ore-forming processes of these two periods constituted the full cycle of the Mesozoic metallogenic explosion of the East Qinling molybdenum ore belt.

Abstract:Abstract: In order to investigate the metallogenic mechanism, ore source and evolution of the Xiachen fluorite deposit in Tiantai basin, the authors studied the geological background as well as trace and REE geochemical characteristics of this ore deposit. The results show that the ∑REE, LREE, MREE and HREE values of wall rocks are much higher than those of ores in the Xiachen fluorite deposit, and REE values of fluorite, quartz and wall rock are characterized by relative enrichment of LREE and depletion of HREE. In addition, (La/Yb）N ratios are mostly higher than 8, and REE patterns show a steeply right-oblique feature. Fluorite has weakly positive Eu anomaly and quartz shows weak negative Eu anomaly. Fluorite and quartz have no significant Ce anomaly. According to the La/Ho-Y/Ho diagram, the ore-forming materials of fluorite were derived from the same source, and fluorite and quartz were formed in the same period. The ore-forming material Ca might have been mainly derived from purple sedimentary rocks in Chaochuan Formation, whereas F was probably derived from both Chaochuan Formation sedimentary rocks and Chencai Group metamorphic rocks. According to the geological characteristics of the ore deposit and the Tb/Ca-Tb/La diagram, the authors hold that the ore deposit is an epithermal fault filling-metasomatic type deposit.

Abstract:Abstract: Based on the core and field section observation and microscopic section in combination with analysis of geology, drilling and physical properties data, this paper discusses in detail sedimentary facies and reservoir characteristics of Da'anzhai member in eastern Sichuan Basin. The division scheme of sedimentary facies in Da'anzhai member is put forward, which argues that the transitional parts at the edge, on the slope and on the semi-deep lake biasing deep lake side are favorable for developing heterogeneity and shale gas (oil) reservoirs, that reservoirs of Da'anzhai member in the study area belong to ultra-low porosity and permeability pore fracture type reservoirs, whose reservoir space comprises of fracture, intracrystalline pore, eroded micro-pores, solution openings and dissolved caves, dominated by fractures, with solution openings and dissolved caves taking the second place. In addition, compaction, pressure solution, cavity filling, silicification and cementation are main factors adversely affect reservoir quality, while dissolution and rupture process improve reservoir quality. Therefore, The development of reservoirs in Da'anzhai member is not only controlled by sedimentary facies, rock type, diagenesis and tectonics but also affected by content of organic carbon, maturity of organic, brittle mineral content, thickness and buried depth of shale in the study area.

Abstract:Abstract: The Minfeng area is a vital part in oil and gas exploration of Dongying depression, and the analysis of source system has much significance in the study of sedimentary system and reservoir evaluation. Ancient landscape controlled the fundamental pattern of the distribution of the sedimentary system, whereas the downthrow side of Chennan fault, the interior of Minfeng sag and the Xinzhen area provided the accommodation space for the deposition of sand bodies. Characteristic elements and sandy disperse system suggest that, during the period of the generation of middle-lower 3rd Member of Shahejie Formation (Es31-2), there were three source systems around the Minfeng area, and the sedimentary primitive components came from Chenjiazhuang salient in the north, Qingtuozi salient in the east and the external basin water system through Guangrao salient, and the main fractures of F1 and F2 of Xinzhen structure might have served as the main source channels in southward direction. The southern part of the sedimentary system controlled by the eastern source system met the northern branch of the southern source system. The primitive sedimentary components constituted the foundation of the reservoir, which caused the differences in the reservoir space and physical properties. The reservoirs in the facies belt of the delta front in the east and the mixed resource area are characterized by weak compaction with well-developed primary intergranular pores and have favorable porosity and permeability with high oiliness, thus superior to the physical properties of reservoirs in the south and north，with the reservoirs in the mixed-resources area having the best oiliness.