Abstract:Abstract: Northwestern China lies in the intersection region between Central Asia and Tethyan tectonic domains, with Tarim craton and western North China craton in the middle. The formation and motion of the two cratons and their cracked micromassif formed during geological evolution basically constrained the process of tectonic development in Northwest China. The Phanerozoic orogenic belt surrounding cratons and micromassif resulted from peripheral accreting, with the addition of other products of continental edge accreting during continental convergence at about 210 Ma because of continental migration. All orogenic belts and continental edge accretions constituted very important formation settings of endogenic metallic ore deposits in Northwest China. In recent years, the newly discovered ore deposits in Northwest China have confirmed the idea that magmatic mineralization resulted from craton edge tectonic accreting and intraplate mantle magmatism, which challenges traditional understanding of geological tectonic settings. Among these deposits, three large or superlarge deposits, i.e., early Carboniferous Awulale volcanic-subvolcanic magmatic outpouring type magnetite deposit of Western Tianshan Mountains, early Devonian Xiarihamu magmatic Ni-Cu sulfide deposit of eastern Kunlun Mountains and Jurassic-Cretaceous Huoshaoyun tectonic hydrothermal Pb-Zn deposit in western Kunlun Mountains, have especially important economic value and geological implications. Awulale is the first volcanic-subvolcanic magma outpouring type magnetite deposit in China, which is comparable with the Laco superlarge magnetite deposit in Chile, and hence the exploration and study of Awulale are of great importance for understanding deeply rifted volcanic magmatism and mineralization of Carboniferous in Tianshan and its adjacent areas of Central Asia Orogenic Belt. The Xiarihamu magmatic Ni-Cu sulfide deposit with one million tons of Ni metal is also very important, and its discovery provides a research area for magmatism and mineralization in the early Paleozoic Ni metallogenic event and its prospecting potential. The discovery of the Huoshaoyun Pb-Zn deposit with superlarge reserves is a very important discovery in Mesozoic giant Pb-Zn metallogenic belt of the Kunlun-Sanjiang orogenic belt. These discoveries supply new basis for the understanding of ore-forming material source and structural control of ore deposits in the giant Pb-Zn metallogenic belt on the northeastern margin of the Tibetan Plateau.

Abstract:Abstract: Western Tianshan Mountains extend from Uzbekistan through Tajikistan, Kyrgyzstan, southern Kazakhstan to Xinjiang Western Tianshan, with a length of 2500 km from west to east. This belt is the core zone of the “Asian Gold Belt” and shows evident potential of Au-Cu-Zn-Pb mineral resources. Large Au-Cu-Zn-Pb ore deposits are expected to be found in Western Tianshan of Xinjiang. Based on consulting various references and thoroughly investigating the regional geology and mineral resources in western Tianshan, the authors hold that the important mineralizations of Au-Cu-Zn-Pb ore deposits include such types as orogenic Au, porphyry Au-Cu, SEDEX and sandstone Zn-Pb. The orogenic Au deposits formed in two geological environments in the Paleozoic, the porphyry Cu deposits formed in the mature island orc environments of various periods in the Paleozoic, the SEDEX Zn-Pb deposits occurred in the continental margin basin of the Neoproterozoic, and the sandstone Zn-Pb deposits occurred in the foreland basin of Mesozoic-Cenozoic period. The metallogenic environment and the ore-forming types are all favorable for the Au-Cu-Zn-Pb mineralization in Western Tianshan and show promising potential for ore prospecting. The large Au-Cu-Zn-Pb ore deposits could be found continuously in Xinjiang Western Tianshan, China. The results obtained by the authors provide reference and indication for regional metallogenic understanding and Au-Cu-Zn-Pb ore exploration.

Abstract:Abstract: The Asian gold belt extends into Western Tianshan Mountains, showing great prospecting foreground and potentiality. The Katebasu gold deposit is a newly-discovered large-sized deposit, with 87t gold reserves and 3.84 g/t average gold grade. The deposit is situated in a deformation band near the north Nalati fracture on the northern margin of the Middle Tianshan Mountains. Gold orebody, lenticular or tabular in form, is controlled by the alteration zone along with the brittle and ductile fracture zone in the monzonite granite. The center of the gold orebody is silicified rock with gold-bearing pyritization, and the edge is sericite chlorite epidote altered rock with gold-bearing pyritization. The pyrite and chacopyrite are main gold carriers, with ionic gold in pyrite, while embedded-gold and fissure-gold constitute the main forms in chacopyrite. The geological bodies of the Katebasu large-sized gold deposit consist of monzonite granite, with a (346.3±3.3) Ma zircon U-Pb concordia age, suggesting Early Carboniferous. The isochron age of the ore-bearing pyrite is (310.9±4.2) Ma, implying Late Carboniferous, appximately 35 Ma later than monzonite granite. The key to gold mineralization was the tectonic fluidization caused by the closure of South Tianshan Ocean and the collision of Tarim plate with Middle Tianshan landmass. Ore-forming fluids of gold were mesothermal to hyperthermal (270~390 °C) and low-middle?salinity (7%?16% NaCl eq.) ones rich in CO2, with the data δ18O[H2O](V?SMOW)=1.6‰?6.4‰ and δD [H2O](V?SMOW)=?64‰ ?107‰, showing characteristics of deep metamorphism fluids. The average (187Os/188Os)i of the pyrite in gold ore is 1.449±0.052, and the REE patterns and Pb isotope (206Pb/204Pb=18.129?18.773, 207Pb/204Pb=15.459?15.554, 208Pb/204Pb=37.707?38.123) have similarity or relevance to the earth crust of the Middle Tianshan Mountains, suggesting that the metallogenic material was derived form the earth crust. The δ34S values of the sulfide are 6.92‰?12.15‰, implying that the S of the ore came from Thermochemical Sulfate Reduction (TSR) of the marine strata of Paleozoic. The Katebasu gold deposit was controlled by the shatter tectonic stresses between the Tarim plate and the Middle Tianshan zone in Late Carboniferous epoch, produced by the structure-altered Tianshan rock and belonging to the collision-orogeny gold deposit. The results achieved by the authors provide valuable guide for the continuous prospecting breakthrough in Western Tianshan Mountains of Xinjiang.

Abstract:Abstract：The superlarge Xiarihamu magmatic Ni-Cu sulfide deposit is located in eastern Kunlun orogenic belt of Qinghai Province. The study of its mineralization, lithology, geodynamic mechanism and tectonic setting is very important for further prospecting breakthrough in eastern Kunlun orogenic belt. This paper discusses the tectonic setting of the mineralization in Xiarihamu magmatic Ni-Cu deposit through the dating of Xiarihamu mafic-ultramafic intrusion, and further indicates the prospecting significance and potentiality of eastern Kunlun region. Most magmatic sulfides were found in peridotites and pyroxenites through drilling, and the Ni-bearing ultramafic intrusion orebody is different from the gabbro in the formation time. The zircon U-Pb ages of barren olivine-pyroxenite from Xiarihamu ultramafic intrusion drilling core are 412.9±1.8 Ma（MSWD=1.2）and 410.9±1.6 Ma（MSWD=3.1）, about 20 Ma younger than the age of gabbro. It is revealed that parent magma had the island arc magma characteristics, as shown by systematic olivine composition and Fo value study of Xiarihamu ultramafic intrusion drilling core samples. Based on these data, together with the age of eclogite in this region, the authors preliminarily hold that the magma source of Xiarihamu ultramafic intrusion had the characteristics of eastern Kunlun island arc. There occurred sulfide immiscibility of silicate magma with the upwelling of the partial melting magma, and the differentiated magma intruded into the structurally weak location of post collision in eastern Kunlun orogenic belt and formed the superlarge Xiarihamu magmatic Ni-Cu deposit. The crustal contamination of S played a very important role in forming the Ni orebody. This understanding is of great prospecting significance and research value for mineralization evaluation and potentiality exploration around other mafic-ultramafic intrusions in eastern Kunlun orogenic belt.

Abstract:Abstract：The medium-sized Baixintan Ni-Cu deposit is located at northern Dacaotan fracture, Eastern Tianshan Mountains. The intrusion is emplaced in middle Ordovician Qiaganbulake Group, and the direct country rocks are dacite and tuff. The Baixintan deposit mainly consists of gabbro, olivine pyroxenite and wehrlite, with wehrlite being the main ore-bearing rock type. Orebodies are mostly in bedded or lenticular form. From the center outwards the basicity shows a decreasing trend. Zircon U-Pb La-ICP-MS age of plagioclase-bearing wehrlite is (277.9±2.6) Ma, suggesting Early Permian. With No. 24 exploration line as the dividing line, the Cu/Ni ratio of western orebody is higer than that of the eastern orebody. The values of MgO and FeOT show positive correlation, and there is a negative relationship between MgO and SiO2, CaO and TiO2. The m/f ratio is between 2.43 and 3.9, belonging to the iron series ultramafic rocks. Chondrite-normalized REE patterns show LREE enrichment and negative or no Eu anomaly. The rocks are enriched in LILE and depleted in HFSE (Nb, Ta). The fractionation crystallization/cumulation was dominated by olivine and pyroxenes in the process of magmatic evolution. The geochemical features of analyzed rocks indicate that the parental magma of the rocks experienced weak contamination by middle-lower crust components during its upward migration. The magma source was metasomatized by subduction fluid. The chronological and geochemical characteristics, together with regional evolution history of Earsten Tianshan area, indicate that the Baixintan Cu-Ni deposit might be the product of post-collision extension and mantle plume activities. There is still huge potential for Cu-Ni mineralization on the weatern side of the Huangshandong-Jingerquan-Tulargen Cu-Ni ore belt. The Dacaotan fracture may be another main structure which controls the mafic intrusion and the Ni-Cu deposit.

Abstract:Abstract: Permian large-sized mafic-ultramafic complexes such as Pobei, Luodong, Bijiashan, Hongshishan and Xuanwoling, are developed as a cluster in Beishan area, Xinjiang. They are mainly composed of peridotite, pyroxenite and gabbro. They have significant cumulate rhythmic layers of magmatic minerals, and are commonly considered to be layered mafic-ultramafic intrusions hosting Ni-Cu sulfide deposits. Their intrusive ages (260.7-289 Ma) are close to the age of the Tarim large igneous province. Beishan layered mafic-ultramafic intrusions show positive correlation between Fo values and Ni content of olivine minerals. Their trace elements are characterized by negative anomalies of high field strength elements (Zr, Hf, Nb, Ta and Ti), and richness of Rb, Sr and Pb in comparison with the primitive mantle (PM). They have LREE-depleted-flat rare earth element (REE) patterns. The rocks display low PGE content and IPGE-depleted PGE primitive mantle normalized distribution patterns. The Sr, Nd isotopes are located between depleted mantle (DM) and OIB ranges, whereas Re-Os isotopic compositions overlap the ranges of mantle plume magmatic Noril’sk Cu-Ni sulfide deposits and Emeishan basalts. Simulated calculations show that the parental magmas of Beishan complexes had high MgO content and high magmatic initial liquidus temperature and crystallization temperature, and underwent fractional crystallization and different degrees of crustal contamination in their evolution process. Parental magma experienced sulfide segregation in the mantle source or during the emplacement, and resulted in depletion of PGE. It is inferred that large-sized mafic-ultramafic complexes in Beishan area were formed by high degree of partial melting of lithospheric mantle modified by subduction fluid at high temperature due to lithosphere delamination and asthenosphere upwelling triggered by a superposed mantle plume in a post-collisional extension tectonic setting, and thus show large metallogenic potentials for the formation of magmatic deposits.

Abstract:Abstract: The newly-discovered Niubiziliang Ni-Cu deposit is located in the intersection part of the Altum southern fault zone and the Qaidam northern fault zone, Northwest China. There are three mafic-ultramafic intrusions, of which No. Ⅱ and No. Ⅲ intrusions are Ni-Cu sulfide-bearing intrusions. The intrusions consisted of, from the south to the north, peridotite facies, pyroxenite facies and gabbro facies. The peridotite facies contains hornblende lherzolite, hornblende peridotite, lherzolite and plagioclase lherzolite, the pyroxenite facies contains olivine websterite and websterite, and the peridotite facies consists of Ni-Cu bearing rocks. High-precision LA-ICP-MS zircon U-Pb dating yielded the concordant ages of 388.0±2.8 Ma, 402.2±2.8 Ma and 402.8±2.6 Ma for diorites of No.Ⅰ intrusion, lherzolites of No.Ⅱ ore-bearing intrusion and plagioclase lherzolite of No. Ⅲ ore-bearing intrusion, respectively. Regional tectonic evolution background indicates that the Niubiziliang rocks were formed in a post-orogenic extension environment in early Devonian and that the magma originated from mantle material. The Niubiziliang mafic-ultramafic intrusions are new type rocks containing nickel mineralization, and they have good potential for Ni-Cu sulfide exploration.

Abstract:Abstract: The Yushenkala pluton is located in the northern part of west Junggar Basin of Xinjiang and lies along the suture zone between Siberia plate and Junggar plate. Petrologically, the pluton consists of gabbro, hornblende gabbro, diorite and quartz diorite which intruded in the middle Devonian Yudoukala Group. LA-ICP-MS zircon U-Pb dating shows that the age of the hornblende gabbro is 364±1Ma, which represents the formation age of the pluon. The εHf (t) values of the zircon are in the range of 4.3-11.5, with a weighted average of 9.0±1.2, suggesting that its original rock was derived from mantle materials. The one-stage Hf model ages (TDM1) are 529-827 Ma (629±95 Ma on average), indicating an original rock of Cambrian - Precambrian basement. Based on field geological and geochemical characteristics, the authors infer that the pluton formed in an island-arc environment or active epicontinental environment. In the late Devonian, the arc magmatism was well developed, and the ocean-continent subduction event basically came to an end in the northwestern part of western Junggar. These data indicate that the closing time of Paleo Asian ocean was not earlier than 364 Ma.

Abstract:Abstract: The Dashuigou gold deposit is located in the middle segment of Eastern Kunlun, and nine orebodies were delineated in the west of the Dashuigou gold deposit. In combination with geochemical anomalies and regional geological background, the authors hold that the Dashuigou gold deposit has good ore-search prospect. Gold ore prospecting has achieved new breakthrough. LA-MC-ICPMS zircon U-Pb dating shows that the weighted mean age of tonalite, which is closely related to mineralization in the Dashuigou gold deposit, is (239.5±0.9)Ma, with MSWD being 1.3, suggesting Middle Triassic. Geochemical studies indicate that tonalite belongs to the calc-alkaline series, with obvious fractionation of REE, enrichment of LREE and slightly negative Eu anomalies. This suite of rocks are enriched in LILE (such as Rb, K), LREE and more mobile incompatible elements (such as Th), and relatively depleted in HFSE (such as Nb, Ta, Ti, P). Rb/Sr and Nb/Ta ratios reflect the characteristics of mantle-derived magma. Based on a combined study of geochronology, geochemistry and evolutionary characteristics of regional structures, the authors hold that tonalite was formed at the subduction stage. Subduction promoted the migration of mantle-derived fluids, which precipitated in favorable?parts?of?structure, forming the gold orebody.

Abstract:Abstract: Qimantag in East Kunlun Mountains is an important skarn-type iron-polymetallic metallogenic belt in Qinghai Province, and the Xiaoyuanshan iron-polymetallic ore district is located in the eastern Qimantag, Qinghai. The mineralization has close relationship with plagiogranite porphyry, and the orebody occurs in the outer contact zone of plagiogranite porphyry. LA-MC-ICP-MS zircon U-Pb dating shows that the weighted mean age of plagiogranite porphyry is 216.9±1.9 Ma (n=16，MSWD=2.9), suggesting Late Triassic. Detailed petrogeochemical studies show that the plagiogranite porphyry belongs to the peraluminous high-K calc-alkaline series. This suite of rocks are enriched in LILE (such as Rb, K), LREE and more mobile incompatible elements (such as U, Th) and relatively depleted in HFSE (such as Nb, Ta, Ti, P). The plagiogranite porphyry is rich in LREE and poor in HREE, with obviously negative Eu anomalies. Based on a combined study of geochronology and evolutionary characteristics of regional structures, the authors consider that the plagiogranite porphyry was formed at the post-collisional development stage of the orogen, corresponding to the late stage of the Late Paleozoic-Early Mesozoic tectonic event in eastern Kunlun orogenic belt．

Abstract:Abstract: On the basis of rock types, ages and geochemical data of Neopaleozoic and Mesozoic granites, the authors studied the magmatic stages and petrogenesis of these granites, and discussed tectonic magmatic evolution and collision orogenic process of the western West Kunlun Mountains in combination with the regional geological information. The authors have reached the conclusion that the tectonic magmatic evolution of Neopaleozoic and Mesozoic period should be divided into seven stages: (1) 388-324 Ma (northward subduction of Branch I of Tethys Ocean): granites at this stage had TTG rock association with rich sodium and poor potassium, probably formed in an epicontinental arc; (2) 339-291 Ma (Oytag back-arc basin): this back-arc basin was formed by northward subduction of Branch I of Tethys Ocean in the south, and subsequent tholeiitic ocean granites might be characterized by rich sodium and poor potassium; (3) 258-241 Ma (the stage of the closure of Branch I of Tethys Ocean and collision orogeny): the granites of this stage were gneissic S-stye granites with muscovite and garnet which should have originated from continental crust; (4) 234-210 Ma (the post collision extensional stage during TethysⅠ): huge granitic batholiths were I-A style granites which were closely associated with mantle magma underplating and magma mixing; (5) 198-150 Ma (southward subduction of Branch II of Tethys Ocean): granites of this stage had TTG rock association and were formed in continental marginal arc or island arc setting; (6) 148-118 Ma (the stage of closure of Branch II of Tethys Ocean and collision orogeny): monzonitic granites with weak gneissic structure belonged to C style adakites as a result of melting of thickening crust during continental collision; (7) 111-75 Ma (the post collision extensional stage during Tethys Ⅱ): the massive granites belonged to shoshonitic series formed by partial melting of ancient crust. The authors put forward a tectonic evolution model for the western West Kunlun Mountains during Neopaleozoic and Mesozoic based on tectonic magmatic evolution of different stages.

Abstract:Abstract: The genesis of the Late Carboniferous bimodal volcanic rocks in Jijitaizi area of eastern Bogda orogenic belt was revealed recently, which comprise mainly sub-alkaline basalts and subordinately rhyolite rocks, belonging mainly to the tholeiitic series. The basalts have high Al (Al2O3=19.81%-20.60%), low Mg (MgO=2.95%-3.25%, Mg#=32.33-34.50), Na2O/K2O ratios of 2.84-3.01 and TiO2 values of 1.32%-1.43%, slightly higher than values of N-MORB, indicating obvious fractional crystallization of olivene and pyroxene during basaltic magmatism and an evolution product of original magma’s fractional crystallization. They have the following characteristics: Zr/Nb=41.13-41.38, Zr/Y=4.26-4.52 (all higher than 4.00), Rb/Sr=0.02-0.04 (all less than 0.05), Dy/Yb=1.92-2.00, La/Nb=2.42-2.49, Ba/Nb=113.58-126.05, Ba/La=47.02-50.62, slight enrichment of trace elements Rb, Ba and P, slight positive Eu anomalies (δEu=1.02-1.10), and relative depletion of Nb, Ta, Th, Sr and Ti. In addition, the Zr-Nb, La/Yb-Dy/Yb and La/Nb-La/Ba discrimination diagrams indicate that the basalts had geochemical features indicative of intraplate basalts formed within the continent, originated from high degree partial melting of the transition product from depleted spinel phase mantle peridotite to garnet phase mantle peridotite, and suffered a certain degree of crustal contamination during the rising process. The rhyolites of bimodal volcanic rocks have high SiO2 (76.54%-77.74%) and ALK (Na2O+K2O=6.70%-7.70%), but low TiO2 (0.15%-0.16%), Al2O3 (10.70%-10.90%) and MgO (0.17%-0.18%, Mg#=13.93-14.52). Their trace elements generally have features of enrichment of Rb, Th and U, obvious depletion of Sr, P and Ti, and slight depletion of Ta and Nb; the REE distribution patterns are characterized by LREE enrichment, right-oblique form and obvious depletion of Eu (δEu=0.32-0.33), suggesting that the rocks originated from the melting of crustal material with plagioclase as an important relic mineral in the source. Geochemical characteristics of the bimodal volcanic rocks in Jijitaizi area indicate that the volcanic rocks were formed in a typical tectonic setting of continental rift. The rhyolites with LA-ICP-MS zircon U-Pb age of (312±1) Ma suggest that this series of volcanic rocks were formed at the beginning of Late Carboniferous. According to these characteristics in combination with the Rb-Sr and Zr-Zr/Y diagrams, the crust thickness (20.0-30.0 kilometers) and extension speed (2.0 cm/a-5.0 cm/a) might suggest the fast development of Bogda rift, which stared in the Early Carboniferous and reached its culmination at the beginning of Late Carboniferous, and also represent the transitional period of geodynamic environment from collision and compression to stretching and extension. The results achieved by the authors further confirm the view that the Carboniferous Bogda orogenic belt belongs to continental rift and it could provide evidence for understanding the tectonic evolution and plate system of the Bogda orogenic belt of the Late Paleozoic.

Abstract:Abstract: There exist widely-developed volcanic rocks of Dahalajunshan Formation along the Awulale metallogenic belt in West Tianshan Mountains. They are volcano-sedimentary rocks composed mainly of a set of rhyolite, trachyte, trachyandesite and intermediate-acidic tuff as well as a small amount of basalts. In this paper, the authors used LA-ICPMS zircon U-Pb dating method to determine the rock-forming age of volcanic rocks from Songhu, Shikebutai and Beizhan iron ore deposits. In addition, the authors sorted out the high-precision geochronological data previously obtained from the Awulale metallogenic belt. There exists the gradual change regularity from west to east: Chronologically, the age tends to change from old to young eastward, the Early Carboniferous volcanic rocks tend to pinch eastward, and the lithologic character varies in order of andesite lithology - basaltic andesite - rough endoplasmic lava - pyroclastic rocks. On the basis of data obtained and remote sensing image features, the authors determined the temporal and spatial distribution of the volcanic rocks in Dahalajunshan Formation, extracted the characteristics of the caldera and judged the spatial relationship between typical ore deposits and the caldera, thus investigating the genetic relationship between typical deposits and volcanic apparatuses. In combination with tectonic evolution characteristics, the geological significance is also discussed.

Abstract:Abstract: The Wuluate Formation of Lower Carboniferous is distributed in the northern part of Western Kunlun Mountains. Associated with thick carbonate?rock?and thin? marble, it is a set of volcano-sedimentary rocks mainly?composed of grayish green?pillow basalts and grayish?white rhyolite. Based on the study of the chemistry of lavas, the authors hold that the major element values of the basalts are similar to the average values of tholeiite: SiO2 values vary between 52.10% and 54.42%， (Na2O/K2O)>1，TiO2(0.50%~2.03%)，and Mg# values are in the range of 52~70. The ΣREE values of the samples range from 14.46×10-6 to 91.83×10-6，whereas (La/Yb)N values vary between 0.46 and 1.69，respectively. All these characteristics are extremely similar to things of the E-BABB and different from features of OIB and N-MORB. The basalts show depletion of Rb, suggesting that the lower crust contamination existed in the magma processing. Rhyolite belongs to both calc-alkaline and high-K calc-alkaline volcanic rock series. Concentrations of REE are higher than those of basalts, the (La/Yb)N radios are between 1.30 and 11.99, and (La/Sm)N radios are from 1.15 to 4.07. All these features are similar to features of the lower crust. Different REE patterns and trace element features between the two rock types and the absence of trend from the basalts to the rhyolite imply that the rhyolite and basalt had different sources and origins. Trace element diagrams and regional geological characteristics indicate that the Wuluate Formation formed in an extension environment of the back-arc pull-apart condition. The study of the genetic characteristics of rocks suggest that the basalts resulted from 5% –10% partial melting of spinel lherzolite in the depleted mantle, and were contaminated by the lower crust later. The heat carried by the mantle material led to the partial melting of the lower crust, and then the rhyolite was produced. Comprehensive studies show that the northern part of Western Kunlun Mountains was in a stretch tension environment (back–arc extensional environment) in the early Carboniferous, and the Wuluate Formation was the magmatic product of the tectonic event.

Abstract:Abstract: The Yingou Group is mainly distributed in Sunan area of North Qilian orogenic belt and consists of intermediate-basic volcanic rocks, pyroclast intercalated with silicalite, metamorphic mudstones and sandstones. U-Pb ages of detrital zircons from two sandstone samples in the Upper Yingou Group were measured using the LA-ICP-MS method. The ages of the youngest zircons, (425±2) Ma and (425±5) Ma, indicate that the deposition took place in the Early to Middle Silurian. Therefore, the age and the composition of the Yingou Group should be redefined. The concordant ages of detrial zircons show that the provenance in the Upper Yingou Group was derived mainly from the Central Qilian block (800-1000 Ma, 1600-1800 Ma), subordinately from the North Qilian arc and synorogenic granites (425-510 Ma), and rarely from the North China plate (＞1800 Ma).

Abstract:Abstract: The Bulunkuole Group is one of the main components of Taxkorgan landmass in the Western Kunlun area, and is also important ore-bearing strata of the regional iron deposits. Recently, many large-sized iron deposits were found within the Bulunkuole Group, such as Zankan, Laobing, Mokaer and Yelike iron deposits. On the basis of detailed?petrography?features and SHRIMP U-Pb zircon dating of metamorphic rock and magmatic rock in the intrusion strata of the Bulunkuole Group from the Zankan iron deposit, the authors discussed the formation age of ore-bearing strata, and investigated the ore-forming age. The results show that the formation age of the representative magmatic zircon from plagioclase-hornblende schist in Bulunkuole Group is (1845.0±11.0) Ma, suggesting that ore-bearing strata are younger than (1845.0±11.0) Ma. Zircon SHRIMP dating of plagiogranite porphyry that intruded into the strata yielded a U-Pb age of (544.5±4.7) Ma, suggesting that the ore-bearing strata are older than (544.5±4.7) Ma. Thus the ore-bearing strata were formed during 1845.0?544.5 Ma. Moreover, SHRIMP dating of the zircon core from dacite yielded U-Pb ages of 3048.0?3054.0 Ma and 2032.0 Ma, indicating that there possibly exists an early Proterozoic or Archean basement in the surveyed area and adjacent areas, which is of important significance for recognizing Bulunkuole Group and the basement of Taxkorgan landmass. Bulunkuole Group outcropped in Taxian-Waqia uplift zone is one of the earliest strata in Western Kunlun Mountains, and this provides a basis for the existence of Taxkorgan paleo-landmass. Comparative researches on different types of deposits indicate that the Zankan iron deposit was mainly produced by the sedimentary mineralization process, and iron bodies with iron-bearing rocks of Bulunkuole Group were syngenetic, and hence the mineralization age of the Zankan iron deposit is Proterozoic, which is in accordance with the formation age of Bulunkuole Group and is also a very important period for the generation of global iron deposits.

Abstract:Abstract: The Hutouya Pb-Zn polymetallic ore deposit is located in Qimantag, East Kunlun. Intermediate-acid intrusive rocks occur widely in this area, and are closely related to iron polymetallic mineralization. The results of LA-ICP-MS zircon U-Pb isotope dating reval that the granodiorite in the periphery of No. Ⅴore belt was formed at (224.3±0.6) Ma and the orthoclase granite in No. Ⅷ ore belt was formed at (239.7±0.8) Ma. Petrogeochemistry shows that the granodiorite is rich in K and poor in Na, with no strong negative Eu anomalies (δEu=0.68-1.06), and is enriched in Rb, Th, U, K, but depleted in Nb, P, Ti, thus belonging probably to I-type granite series. The orthoclase granite is characterized by high SiO2, high alkali, low TFeO, MgO, CaO, P2O5 and TiO2, strong negative Eu anomalies (δEu 0.08-0.26), enrichment of Rb, Th, U, K，and depletion of P, Ti, Ba, Sr, belonging probably to highly fractionated I-type granite series. Both of them were formed at the post-collision stage. Variable Hf isotopic compositions of zircon indicate that it experienced magma mixing, which provided large quantities of ore-forming meterials for large-scale polymetallic mineralization.

Abstract:Abstract: The porphyritoid dioritic enclaves are widely distributed in granodiorites of the Kaerqueka copper deposit, East Kunlun belt. The enclaves are mostly aligned ovals, with similar mineralogy to the host rocks. However, the modal percentage of hornblende is significantly higher than that of the host rock. It has apparent imbalanced structure with development of needle-like apatite. The granodiorite and enclaves have the same age of 234 Ma, which indicates that they might have been formed by magma mixing. As for geochemical characteristics, the enclaves contain higher values of SiO2 and MgO than the host rock and are hence more mafic. They are also enriched in large LILE and LREE, and are depleted in HFSE. The LaN/YbN ratios of host granodiorite (11.6?19.0) are significantly higher than the ratios of the enclaves (5.0?9.7). The Nb/Ta values of host granodiorite (10.6?11.7) are lower than those of the enclaves (11.6?14.8). They have similar Sr, Nd and Hf isotopic compositions. The granodiorite has εNd(t) values of ?5.3 to ?4.2, (87Sr/86Sr)i values of 0.71110?0.71125, εHf(t) values of ?5.8 to ?1.6, tDM(Hf) values of 1012?1102 Ma. The enclaves have εNd(t) values of ?5.2 to ?5.0, (87Sr/86Sr)i values of 0.71114?0.71171, εHf(t) values of ?6.3 to ?3.4, and tDM(Hf) values of 937?1129 Ma. These data indicate that, at the subduction-collision transition stage of Triassic period, the enriched EMII type lithosphere mantle underwent partial melting and produced mafic magma under the influence of upwelling asthenosphere materials. The partial melting of lower crust materials, which had been underplated by the mantle, formed the felsic magma chamber. The injection of mafic magma into the felsic magma chamber formed enclaves. After mixing of evolved mafic magma with felsic magma, enclaves-bearing homogeneous magma was formed. The crystallization of this homogeneous magma formed granodiorites containing enclaves.

Abstract:Abstract: The Bielisaibei iron deposit is a small deposit recently discovered in the East Kunlun metallogenic belt. Based on an analysis of the geological background and ore deposit characteristics, the authors studied petrological geochemistry of the deposit and conducted LA-ICP-MS zircon U-Pb dating of the quartz diorite which is most closely related to mineralization. According to the results obtained, the LA-ICP-MS zircon U-Pb age of the quartz diorite is 242.9 ± 0.6 Ma (MSWD = 0.6, n=22), and the major elements of the quartz diorite have the data SiO2 (51.98%-63.83%), Al2O3 (14.55%-17.57%), Na2O (2.95%-4.21%), and K2O (1.60%-3.83%), indicating that the quartz diorite belongs to the metaluminous medium-high potash calc-alkaline series. Other characteristics of the quartz diorite include moderate ΣREE values, enrichment of LREE, moderate negative Eu anomalies, strong enrichment of K, Rb, Th, moderate enrichment of Ta, Nb, Zr, Hf, Ce, Sm, insignificant enrichment of Ba and Sr, depletion of P and Ti, and somewhat higher Sm, Y and Yb values than chondritic values, suggesting that the magma was dominated by crustal rocks.

Abstract:Abstract: Medium- to large-sized gold deposits, such as Dolanasayi, Saidu and Zhelande, are distributed along the southwestern margin of the Altay orogenic belt. In recent years, exploration work has let to the discovery of the Vodok deposit and some other small-sized gold deposits in this belt. These gold deposits mainly occur in the mylonitic quartz diorite. The quartz diorites in the Vodok and the Dolanasayi gold deposits share similar geochemical features, and they are genetically related to a common magmatic activity. On the other hand, the Sarewuzeng tonalite outcropped between the the Vodok and the Dolanasayi gold deposits show very different petrography and structure. LA-ICP-MS U-Pb zircon ages reveal that the gold-bearing quartz diorite in the Vodok deposit and Sarewuzeng tonalite crystallized at (299.4±4.1) Ma and (317.7±1.5) Ma, respectively, indicating that the quartz diorite and the tonalite were formed at post-orogenic and post-collision settings individually. The age of gold-bearing quartz diorite in the Vodok deposit constrains the lower limit of the formation age of the Dolanasayi gold deposit. In combination with previous studies and the age obtained in this study, the mineralization of the Vodok and the Dolanasayi gold deposits most probably took place at about 290 Ma. The Sarewuzeng tonalite was emplaced earlier than the gold mineralization and was of no significant relationship with gold mineralization in this area.

Abstract:Abstract: Located in the Lenglongling volcanic belt of North Qilian Mountain, the Langlike copper deposit is a medium-sized deposit with mineralization mainly occurring in quartz dioritic porphyrite. Based on an analysis of the mineralization features of the deposit, the authors used the zircon LA-ICP-MS U-Pb and molybdenite ICP-MS Re-Os highly precise dating techniques to study the ore-bearing quartz dioritic porphyrite and five samples of molybdenum collected from the deposit. Zircon U-Pb dating yielded an age of (461.5±7.3) Ma for quartz dioritic porphyrite. The Re-Os model ages of the molybdenite samples vary from (467.1±6.3) Ma to (471.3±6.7) Ma and the Re-Os isochron age is (470.5±3.4) Ma. The similar zircon U-Pb and molybdenite Re-Os isotopic ages suggest that the Langlike copper deposit formed in middle Ordovician and it had a close temporal relationship with the quartz dioritic porphyrite. Combined with the tectonic evolution of the North Qilian, the authors hold that the deposit was produced in an island arc tectonic setting triggered by slab subduction and was similar to the porphyry deposit. These characteristics are of important significance for investigating the genetic type of the Langlike copper deposit and for further prospecting work.

Abstract:Abstract: The Haxiyatu iron-polymetallic deposit is one of the typical deposits with the contribution of mantle-derived components in East Kunlun region. The authors carried out LA-ICP-MS zircon U-Pb dating of main and trace elements in the granite porphyry. LA-ICP-MS dating of zircons from the quartz diorite yielded an age of 246.8±1.8 Ma (MSWD=0.074), suggesting that the rock was formed in middle Triassic and should belong to metaluminous high potassium calc alkaline series, characterized by obvious fractionation of REE, enrichment of LREE and slightly negative Eu anomaly. The granodiorite is enriched in LILE (such as Rb, Ba and K), and relatively depleted in HFSE (such as Ta, Nb and Ti). According to lithological and geochemical characteristics as well as geotectonic background in the same period, the granodiorite was probably produced in Mesozoic magmatic arc environment, with the same source material from the crust-mantle mixing as the quartz diorite. In other strata of skarn mineralization potential, due attention should be paid to granodiorite mineralization in future prospecting work.

Abstract:Abstract: The Xiarihamu Cu-Ni sulfide deposit is a magmatic liquation type deposit discovered for the first time in East Kunlun orogenic belt. This kind of ore deposits is one of the research directions of prospecting for Cu-Ni deposits in Qinghai Province. Based on a study of the metallogenic characteristics of the Xiarihamu Cu-Ni sulfide deposit, the authors hold that the collisional extension environment constituted the basic condition for the formation of the Xiarihamu superlarge Cu-Ni sulfide deposit, the rock-forming and ore-forming processes took place exclusively in early Devonion, and the rock body was emplaced in Paleoproteerozoic Baishahe Formation of Linshuikou, with the addition of the later hybridization mineralization. Based on an analysis of the metallogenic conditions of the magmatic liquation type Ni deposits on the southern and northern margin of Qaidam Basin, the authors have also found that the Devonian thermal event indicated that collisional extension occurred on both the southern margin and the northern margin in this period, the ore-forming mafic-ultramafic rocks on both margins intruded into old strata, stratigraphic sulfur took part in the ore-forming process, and the ore-forming mafic-ultramafic rock bodies are consistent with the geophysical magnetic anomalies as well as Ni, Co, Cu combinational anomalies. An integrated analysis shows that the prospecting potential for magmatic liquation type Ni deposits on the southern and northern margin of Qaidam Basin is great. It is also pointed out that the key prospecting targets in this region is the central kunlun magma arc belt on the southern margin of Qaidam Basin, the high-pressure metamorphic belt on the northern margin of Qaidam Basin, and the Olongbuluck landmass.

Abstract:Abstract：The ferruginous series mafic-ultramafic intrusions have Ni metallogenetic specialization, but mafic-ultramafic intrusions do not necessarily contain Ni ore. Mineralization characteristics can be used to summarize the metallogenic regularity of mafic-ultramafic intrusions and guide the regional exploration. There are 114 mafic-ultramafic intrusive bodies in Hualong area, and their mineralization characteristics and metallogenic regularity are important key factors for exploration breakthrough. The authors studied geological characteristics, geochronology and petrogeochemical characteristics of Yulonggou, Yaqu, Ashengong and Xiashentang intrusions in Hualong area, Qinghai Province, and found that the four intrusions have similar ages, focused in the range of 436Ma~449Ma, probably suggesting the products of the same tectonic setting in southern Qilian orogenic belt. S, Re-Os and Sr-Nd isotopes reveal that parent magma originated from a mantle source which had once experienced metasomatism. Its εNd(t) ratios are -7.74~+8.36, suggesting that the magma source might have been located in the asthenospheric mantle region contaminated by mantle wedge material with subduction plate metasomatism. The rich silicon strata of Hualong rocks group created the condition of assimilation and contamination for sulfide immiscibility, caused the addition of the rich silicon material, formed the sulfide immiscibility, and finally formed the different grades of magmatic Ni-Cu sulfide deposits in the Hualong rock belt, Qinghai Province. Sufficient lithofacies differentiation, enriched olivines and higher basic degree of mafic-ultramafic intrusions were favorable conditions for the formation of Ni orebodies, and could further guide the prospecting work in Hualong mafic-ultramafic intrusive rocks of Qinghai Province.

Abstract:Absract: The late Paleozoic magnetite ore belt is an important iron metallogenic belt in West Tianshan Mountains, Xinjiang. For a long time, there has been controversy concerning the metallogenic setting and genetic type. Based on previous researches in combination with lots of field investigations and indoor studies conducted by the authors in the past three years, this paper deals tentatively with the geological characteristics, distribution patterns and metallogenic types of iron deposits in West Tianshan Mountains, Xinjiang. The Sr-Nd-Pb isotopic compositions of ore minerals show that the metallogenic setting was the island arc under the subduction-collision of ocean and land. The metallogenic age of iron ores was younger than that of volcanic rocks but older than that of intermediate-acid intrusive rocks in the same ore district. The iron material might have come from the volcanic rocks, where their partition models were very similar in trace elements and REE. These iron deposits all belong to marine volcanic type, which can be further divided into three subtypies: volcanic effusion type, volcanic-subvolcanic hydrothermal type, superimposition type of volcanic effusion and volcanic hydrothermal solution. The geological features of different subtype deposits are not different. The iron ores were relatied to the metasomatism of fluid along the zone of subduction. Early iron ores were probably derived from the fractional crystallization of Fe-rich magma after replacement, and the late ores might have resulted from the metasomatism and precipitation of volcanic hydrothermal solution along faults and fractures.

Abstract:Abstract: The Bolong copper deposit is another large-size porphyry deposit discovered after the Duobuza porphyry copper deposit in the Duolong ore district. In this paper, the authors systematically investigated the alterations and vein systems in the Bolong copper deposit based on field geological records and indoor microscopic identifications. The results show that the Bolong copper deposit is characterized by obvious alteration zonation of potassic zone→pyrite phyllic zone→argillation superimposed pyrite phyllic zone→hornfels zone (or propylitization zone on the outer side) from the deep part (core) to the shallow part (or the outer side). Four types of veins (M, A, B, D) can be recognized in the deposit, with A B veins being most developed. the potassic zone, pyrite phyllic zone and A, B veins are related to the mineralization. A comparison with the typical alteration features of porphyry deposits both in China and abroad shows that the alteration features of the Bolong copper deposit are similar to features of the “monzonite” model, and the characteristics of the mineral assemblages are similar to those of the Bajo de la Alumbrera porphyry Cu deposit in Argentina and the Qulong copper deposit and Duobuza copper deposit in Tibet. However, the Bolong deposit has its unique feature that it possesses a large number of sparsely ? densely disseminated and veined magnetites from the potassic zone to the pyrite phyllic zone.

Abstract:Abstract: The Pobei area in Ruoqiang of Xinjiang has drawn much attention among geologists due to numerous magmatic sulfide nickel deposits discovered in this area. The Poyi deposit is a magmatic sulfide copper nickel ore deposit discovered recently. Due to its low grade ore and lack of high grade rich?orebodies, it can not meet?the?requirements?of mineral development. Based on geographic features of mafic-ultramafic rocks on the ntorthern slope, the authors summarized the features of magmatic sulfides already discovered, and made an analysis of favorable ore-forming conditions so as to carry out?ore?metallogenic prediction. In combination with the comprehensive methods for ore exploration which comprise geography, physical exploration, remote sensing and chemical exploration, the authors made a pretty good progress through practice: the anatectic penetration type Podong Ni deposit was discovered for the first time in Pobei area.

Abstract:Abstract: The ultrabasic rocks in the Qingshuiquan area of Eastern Kunlun Mountains have been altered into serpentinite, in which the zonal texture of some chromites provides important information concerning the alteration and evolutionary process of the rocks. The result of electron microprobe analysis shows that the girdle of chromite is composed of three parts, i.e., alumo-chromite, ferri-chromite and chrome-magnetite, from core to rim, respectively, and all of them were wrapped in chlorite. From the alumo-chromite to the ferri-chromite, the Cr2O3, Al2O3, MgO and Mg# values decrease, while the Fe2O3, FeO, TiO2 as well as Cr# and YFe values increase. The authors hold that, along with the serpentinization and regional metamorphism as well as hydrothermal fluid activity, the chromite went through a process in which the temperature was decreasing and the oxygen fugacity was increasing. And then the zonal texture was formed. This process corresponded to another one during which the host rock of the chromite moved upward from the mantle to the crust, accompanied by metamorphism.

Abstract:Abstract: Based on available drilling data of the Xining geothermal field and regional geothermal and geological data in combination with research results of recent exploration projects, the authors analyzed burial conditions, recharge and runoff discharge conditions, geo-temperature field and geochemical characteristics of the Xining geothermal field, and pointed out that the Xining geothermal field mainly has terrestrial heat flow as the heat source, the strata with low thermal conductivity accumulate the heat, the deep circulation gradual heating forced convection mechanism causes the water control and heat control, dominated by basin conduction type planar thermal reservoir, with some characteristics of fracture convective banded thermal reservoir. The thermal reservoir method was adopted to conduct evaluation of the geothermal resource quantity of the Xining geothermal field. The heat quantity accumulated in the thermal reservoir of the geothermal field is 9.343×1014 kJ，and the annual exploited heat quantity of the geothermal field calculated by the average well deployment method is 1.12×1012 kJ, equivalent to 3.78×104 t standard coal. According to the scale classification, the Xining geothermal field should belong to the medium type low-temperature geothermal field. The distribution regularity and resource quantity of the Xining geothermal field have been ascertained, which provides an important basis for the rational development and utilization of geothermal resources in the Xining geothermal field.