Search

The central region of Inner Mongolia that straddles across the Central Asian Orogenic Belt(CAOB)and the northern margin of the North China Block, widely develops magmatic Cu-Ni sulfide deposits(or occurrences). The Ebutu Cu-Ni sulfide deposit is one of the large scales and high-grade magmatic Cu-Ni sulfide deposits within this region. The plagioclase-bearing olivine pyroxenite of Ebutu Cu-Ni sulfide deposit was selected as the main research object by systematic mineralogy, petrography, mineralography, zircon U-Pb geochronology, petrogeochemistry and Sr-Nd isotopes to discuss the diagenetic and metallogenic age and petrogenesis of Ebutu mafic-ultramafic intrusions; based on the integration of regional geological data, the metallogenic potential of Ebutu Cu-Ni sulfide deposit was also briefly discussed, in order to provide suggestions for further breakthrough in Cu-Ni prospecting. The results show that the plagioclase-bearing olivine pyroxenite of Ebutu mafic-ultramafic intrusions yields a LA-ICP-MS zircon U-Pb weighted mean age of(326.0±2.1)Ma, belonging to the Early Carboniferous, indicating that it forms in an island arc setting during the Paleo-Asian ocean subducted to the North China Block. The plagioclase-bearing olivine pyroxenite showes SiO2 contents of 44.62%-55.81% with the average of 51.60%, MgO contents of 27.45%-33.10% with the average of 30.32%, and CaO contents of 1.15%-2.22% with the average of 1.61%. They are enrichment in light rare earth elements(LREE), depletion in heavy rare earth elements(HREE)and slightly negative Eu anomalies on the right-leaning chondrite-normalized REE pattern.(87Sr/86Sr)i,(143Nd/144Nd)i and εNd(t)values vary from 0.708 5 to 0.712 3 with the average of 0.710 6, from 0.511 7 to 0.511 8 with the average of 0.511 8 and from -10.57 to -8.07 with the average of -8.91, respectively. Based on the above studies, it is concluded that the parent magma of Ebutu mafic-ultramafic intrusion probably derives from the partial melting for the enriched lithospheric mantle interacted by the subducted slab-derived fluids. The primary magma is mainly high magnesium basaltic magma, which undergoes strong crustal contamination during the ascending emplacement process. Since the addition of the crustal sulfur and the contamination of silicon-rich crust, it results in sulfide segregation and mineralization. Combined with the regional geological data and the latest prospecting finding, it is considered that the deep and marginal part of Ebutu mafic-ultramafic intrusion has high exploration potential, and the next focus of mineral prospecting should be to clarify the direction of magma flow and to find the hidden intrusions and deep magma channel. [ABSTRACT FROM AUTHOR]

West Qinling orogenic belt is one of the most important gold metallogenic belts in China, where large and super-large gold deposits have been found, such as Zaozigou, Jiagantan, Yidinan, Jiamulong and so on. The formation of the gold deposits is closely related to intermediate acidic intrusive rocks. On the basis of summarizing predecessors' achievements, the Jianglongwa rock mass is discovered in Jianglongwa area, Xiahe County, Gansu Province for the first time in field projects. Based on the study of geological characteristics, stream sediment geochemical characteristics and geophysical characteristics of ground high precision magnetic, as well as the characteristics of Jianglongwa rock mass, it is believed that prospecting potential for finding gold polymetallic deposits in Jianglongwa area. Verified by anomalies, mineralized bodies have been discovered. This prospecting approach provides certain reference for the prospecting of similar deposits in the surroundings of Jianglongwa area. [ABSTRACT FROM AUTHOR]

BACKGROUND: The Ahetala copper deposit is located in Arheqi County, Xinjiang Uygur Autonomous Region. It is located in the South Tianshan orogenic belt, northern margin of Tarim Basin. The deposit belongs to a typical skarn type deposit. OBJECTIVES: In order to determine the types of skarn minerals, as well as the metallogenic process and environment of the deposit. METHODS: Based on detailed field and indoor microscopic observations, electron probe microanalysis (EPMA) was carried out to determine the chemical composition of skarn minerals in the Ahetala copper deposit. RESULTS: The results showed that the skarn minerals were garnet, pyroxene, wollastonite, chlorite and epidote. The EPMA results showed that garnets were grossular and andradite. Pyroxene was diopside (Di77.74-95.46), chlorite was minnesotaite. The Mn/Fe value of diopside was 0.00-0.12, indicating the copper mineralization of this deposit. CONCLUSIONS: The skarn of the Ahetala copper deposit is a typical calcium skarn of metasomatic skarn. According to the mineral paragenetic association and metasomatism, the mineralization stages of the deposit can be divided into early skarn stage, late skarn stage (retrograde alteration), oxide stage and early sulfide stage. From the skarn period to the quartz-sulfide period, the metallogenic environment generally underwent changes from the high temperature, high oxygen fugacity, intermediate-acidic, weak oxidizing-weak reducing environment, to the low temperature, high sulfur fugacity, alkaline reducing environment. [ABSTRACT FROM AUTHOR]

BACKGROUND: The Hetian nephrite belt in Xinjiang is the largest nephrite ore belt in the world, with a length of about 1300 km. In addition to white, gray, black and brown nephrite, the Qiemo—Ruoqiang zone, Xinjiang also produces a yellow-green nephrite. There are few studies on the color origin and characterization of this kind of Hetian nephrite, which affects the understanding of the color and genesis of this kind of Hetian nephrite. OBJECTIVES: To understand the color genesis, genetic types and formation age of the yellow-green nephrite in Qiemo—Ruoqiang deposit. METHODS: Electron probe microanalysis (EPMA), backscattered electron (BSE) image, X-ray fluorescencespectrometry (XRF), and high resolution inductively coupled plasma-mass spectrometry (HR-ICP-MS) were used to investigate mineral and chemical composition. The FeO content was determined by titration method to explore its color origin and genetic type, and the zircon U-Pb isotope dating by sensitive high-resolution ion microprobe (SHRIMP) was used to constrain its mineralization age. RESULTS: Yellow-green nephrite in Qiemo—Ruoqiang was predominately composed of apatite, calcite, dolomite, diopside, epidote, sphene and zircon. The yellow-green nephrite whole rock had low total REE (∑REE=2.61-19.1μg/g) with obvious Eu negative anomaly (δEu<0.05), LREE right dipping, and HREE flat pattern. According to the distribution pattern of rare earth and the content of Cr and Ni, it was inferred that it was a magnesia skarn type Hetian nephrite. Compared with other nephrite in the world, the average value of Fe3+/Fe2+ of the yellow-green nephrite in Qiemo—Ruoqiang (average=0.16) overlapped with nephrite in other regions. The ratio is slightly higher (0.07-0.26), while the content of Fe3+ and Fe2+ was not significantly different between the yellow-green nephrite and other color nephrite. The SHRIMP U-Pb dating of zircon in the yellow-green nephrite yielded ages of 461.7±6.1 Ma (MSWD=1.6) and 498.1±4.6 Ma (MSWD=1.16). CONCLUSIONS: The color genesis of the yellow-green nephrite in Qiemo is probably related to the ratio of Fe3+/Fe2+, but not to the content of Fe3+ and Fe2+. The SHRIMP U-Pb dating results of zircon in yellow-green nephrite represent the formation age of the yellow-green nephrite. These new data provide geochronological constraints for the magmatism of Hetian nephrite belt and the tectonic evolution of the West Kunlun orogenic belt. [ABSTRACT FROM AUTHOR]

In order to explore the elevation gradient distribution characteristics of soil organic carbon and active carbon components ( readily oxidizable carbon and dissolved carbon) in the forest surface( 0-10 cm) of the Taibai Mountain in Qinling Mountains, and elucidate the influencing factors of the elevation gradient pattern, a standard sample plot was placed every 50 m along the northern slope of Taibai Mountain, and the contribution of influencing factors to the soil organic carbon and active carbon components was determined by path analysis. The results show that the soil organic carbon, dissolved carbon, and readily oxidizable carbon contents increased as the altitude increased. The soil organic carbon, dissolved carbon, and readily oxidizable carbon content were significantly different between various climate zones, with the greatest amount in the sub frigid zone, followed by the cold temperate, temperate, and warm temperate zones, respectively. Vegetation zone is also one of the factors affecting the soil organic carbon, dissolved carbon, and readily oxidizable carbon contents. It was observed that content was greatest at alpine meadow, followed by the alpine coniferous forest, birch forest belt, mixed forest belt, quercus acacia, and low mountain mixed belt, respectively. The content of soil organic carbon, readily oxidizable carbon and dissolved carbon are closely related to soil temperature, litter biomass, soil bulk density, and clay content. [ABSTRACT FROM AUTHOR]

The Central Orogenic Belt of New Guinea is the youngest orogenic belt in the world and the most important porphyry-type copper-gold mineralization belt in the world. A set of high-magnesium diorite mass developments has been found in the Nabire region of Indonesia, located in the central-northwestern part of the Central Orogenic Belt of New Guinea, providing a good record for detailed study of magmatic processes and mineralization environments associated with ocean subduction. Through field observations and studies of petrology and geochemical characteristics, it was found that the high magnesium diorite was dominated by fine-grained hornblende and plagiobolite, and no olivine traps or trap crystals were found; Rocks have high MgO content (mass fraction, the same below) (4.51%~10.88%), Yb content ((1.16~2.69)×10) and Y content ((11.68~25.09)×10), high Mg value (50.07~72.50), enrichment of large ionite elements, loss of high field strength elements, relatively low Sr/Y and La/Yb values; Combined with the more consistent Nb/La, U/Nb, Th/La and U/Th values, it is suggested that it may have evolved from the interaction of subduction sediment melt with the overlying mantle peridotite and undergoing separation crystallization, which is accompanied by the release of a large number of HO and fluids, increasing oxygen escape; The formation environment of high magnesium andes/diorites is similar to that of porphyry copper-gold deposits, and has a close affinity with porphyry copper-gold deposits, which is a prospecting marker for large porphyry deposits, while the high-magnesium diorites in the Nabire area have been found to have the development of copper-gold mineralization, indicating that the area has the potential to find large copper-gold deposits [ABSTRACT FROM AUTHOR]

Super-magnesium iron mass has been newly discovered in the Liushuquan area at the southern edge of the East Junggar Orogenic Belt in Xinjiang, with a lithographic caste of olivine pyroxene horn amphibolite. The AGE of zircon obtained by LA-ICP-MS zircon U-Pb was (410.9±3.5) Ma, and the formation era was the Early Devonian. The characteristics of petroglyphology show that the main minerals of olivine pyrocite horn amphibolite are horn amphibolite, olivine, monoclinic pyroxene, containing a small amount of orthophopod and oblique feldspar, and the secondary minerals are chromite, spinel, magnetite and so on. The results of the electronic probe analysis show that olivine belongs to the noble olivine series, and the single oblique pyroxene is mainly calcium-rich diopside, the orthophopod is bronze pyroxene, and the horn amphibolite is calcium-magnesium horn amphibolite and magnesium horn amphibolite. Mineral chemical characteristics reveal that the parent magma of the Willow Springs rock mass is a low-degree evolution of high-magnesium labrabra basalt magma, and the mother magma composition has the characteristics of high Mg and Ni, and the magma has a high oxygen escape (△NNO+0.9~△NNO+1.8) and water content (5.1%-7.0%). Comprehensive research suggests that the olivoxene horn amphibolite in the Willow Spring area has the characteristics of Alaskan-type rock masses, and its parent magma is an aqueous high-magnesium lapping basalt magma formed by partial melting of the mantle wedge under the molten fluid of the subduction zone, forming a tectonic environment stretched before the arc, revealing the existence of pre-Devonian crust subduction in the Kalamairi region and experiencing the process of pre-arc expansion and evolution [ABSTRACT FROM AUTHOR]

Huayangchuan uranium deposit in the west of Xiaoqinling intracontinental orogenic belt, the southern margin of North China Craton, is a polymetallic deposit, which is dominated by U and Nb, and associated with Pb and REE. The existing chronological data show that there are two stages of Indosinian and Yanshanian uranium mineralization in Huayangchuan area. In recent years, a large number of U-bearing pegmatites have been found in Huayangchuan mining area. The petrography, mineralogy and U-Pb chronology of zircon and monazite from U-bearing pegmatites located in Caopinggou of Huayangchuan area were carried out. Zircon U-Pb dating in U-bearing pegmatites is(1 922.5±6.0)Ma, and the mineral assemblage of U-bearing pegmatites shows that there is mineralization in diagenetic stage, indicating that Luliangian(2.0-1.8 Ga)uranium mineralization occurs in the process of basement splicing in the southern margin of North China Craton. The monazites in U-bearing pegmatites have high REE contents with obvious fractionation between LREE and HREE, and the chondrite-normalized REE pattern is characterized by a tilt to right with strong negative Eu anomaly, showing the characteristics of late hydrothermal crystallization genesis of highly differentiated magma. Monazite U-Pb age((141.9±1.8)Ma)indicates that there is a superimposed transformation mineralization of the existing U-rich geological body by Yanshanian granite magmatic hydrothermal process. Therefore, in addition to Indosinian uranium mineralization, there are at least Luliangian uranium pre-enrichment integration mineralization and Yanshanian superimposed transformation mineralization in Huayangchuan area. [ABSTRACT FROM AUTHOR]

The research of Tethys tectonic domain shows more and more characteristics of Proto-Tethys, Paleo-Tethys and Neo-Tethys, among which the research of formation and evolution of Paleo-Tethys ocean and its mineralization are relatively weak, particularly when Paleo-Tethys began cracking almostly lackes necessary research. On the basis of the discovery of Xiarihamu super-large Cu-Ni-Co sulfide deposit at the end of Early Paleozoic in East Kunlun, and the characteristics of a number of magmatic Cu-Ni-Co sulfide deposits dating bet ween t he end of Early Paleozoic and early Late Paleozoic in East Kunlun, Southern Qilian and Alkin, it is proposed that they represent the results of Paleo-Tethys cracking. It is believed that after the collision closure for Proto-Tethys ocean in the same period as Paleo-Asian ocean at the end of Silurian, and as a result of mantle plume, the modified asthenosphere is partially melted and the northern margin of Gondwana continent is cracked, which results in the formation of Xiarihamu deposit related to the mantle-derived mafic-ultramafic rock. Turn of Early and Late Paleozoic is the beginning of Paleo-Tethys ocean cracking, and at this time, Qinling-Qilian-Kunlun ocean as the representative of Proto-Tethys ocean has been closed. Although Paleo-Asian ocean as a back-arc basin of ProtoTethys is not yet closed, Xiarihamu deposit is the product of the re- cracking of continental crust after Proto-Tethys orogeny, and is not formed in the environment of Proto-Tethys island arc or post- collision. Mineralalogy and geochemical results show that although the arc magma information with depletion of Nb, Ta, Ti in Xiarihamu deposit, it is significantly different from A laska rock body in the island arc environment; Xiarihamu deposit has more pyroxenite, less magnetite content, and primary magma with high-Al2 O3, etc. According to the existing mineralization, combined with the research of closed ophiolites and shell subduction returning eclogite of Proto-Tethys ocean, and the characteristics of the regional unconformity of Early Devonian formation and the distribution of bimodal volcanic rocks contemporary with the magmatic Cu-Ni-Co sulfide deposits in East Kunlun, the Early Devonian magmatic Cu-Ni-Co sulfide deposit represented by Xiarihamu deposit is not only the first super-large magmatic Ni-Co sulfide deposit discovered in the global Tethys metallogenic domain, but also represents the new magmatic Cu-Ni-Co important ore-forming event, which is the product of the major geological event of Paleo-Tethys cracking. Strengthening the research of deep magmatic sources and ore-forming processes of mineralized and not syn-exhumation mafic-ultramafic rocks in the orogenic belts, will help revealing the geodynamics mechanisms and processes of the initial tectonic evolution of Paleo-Tethys ocean. [ABSTRACT FROM AUTHOR]

In order to unde rstand the diagenetic sequence, petrogenesis and prospe cting prospect of Tangshe complex pluton in the northeastern margin of Jiangnan orogenic belt, the regional geological mapping, LA-ICP-MS zircon U-Pb age, and all-rock geochemical a nalysis were studied. According to the geological contact r elationship, the diagenetic sequence of Tangs he complex pluton from early to late is determined as medium grained monzonitic granite, medium- coarse grained syenogranite, coarse-medium grained porphyritic syenogranite and fine grained syenogranite, respectively, and the diagenetic ages are (140. 4±3. 3), (131. 7 ±3. 2), (132. 2± 1. 6), and 025. 0±2. 0)Ma. The rocks have the characteristics of high Si and alkali, low P and Ti, being metaluminum-weak peraluminous and high-K calc-alkaline series, which belong to I- type granites. In addition, the light and heavy rare earth elements are highly differentiated, and the chrondrite-normalized REE pattern leans to right with the enrichment of Rb, Th, U, and K, the depletion of Ba, Nb, Ta, Sr, P, and Ti, and the medium-strong negative Eu anomaly. Generally, the magmatic evolution from early to late shows that the contents of SiO2 and K2O, the ratio of K2O/ Na2O, and A/CNK gradually increase, the contents of TiO2, Al2O3, TFeO, MgO, CaO, P2O5 gradually decrease, negative Eu anomaly gradually increases, and the degree of differentiation gradually increases. Tangshe complex pluton is the product of anticline tectonic emplacement after crystal-separation of the remelting of lower crustal material in the inland tension environment after the subduction-collision orogenic of paleo-Pacific plate. Types of mineralization and minerals in the contact zone of Tangshe complex pluton are characterized by W---+Ag-Pb-Zn---+Sb/fluorite zoning from inside to outside, which form a skarn-hydrothermal vein- type mineralization system with a good prospecting prospect. [ABSTRACT FROM AUTHOR]

The southeastern margin of Tibetan Plateau is located at the lateral convergence between Indian plate and Eurasian plate, which is an ideal place to test the geodynamic model of the collision orogen. The present geophysical and Cenozoic magmatic rock data in this area were collected as comprehensively as possible, and the indication of these data on the structure and composition of the collision orogen was discussed. It is suggested that there are great differences in the structure and composition of crust and mantle in different parts of the southeastern margin of Tibetan Plateau. Low-velocity layers are generally developed in the middle crust (the depth is 15-30 km) of Lan ping-Simao, Baoshan and Tengchong blocks, indicating the existence of waterrich or partial melting material layers, which makes it possible for the material of Tibetan Plateau to flow to the southeast. The high-Sr and low-Nd leucogranite dykes in the large shear zone are derived from above partial melting layer. However, Yangtze plate develops a high-velocity body at the same depth, and its composition is likely to be Emeishan basalt, which blocks the material flow in the collision zone. High-velocity bodies with banded distribution appear at the bottom of the lower crust of both Yangtze plate and Lanping-Simao block. According to the characteristics of the lower crust source area shown by Cenozoic high-Sr and low-Y rocks, and combined with the geological evolution history of this area, these two high-velocity bodies are interpreted as Neoproterozoic mafic arc magmatic rocks and Permian-Triassic mafic arc magmatic rocks, respectively. The mantle anisotropy in the southeastern margin of Tibetan Plateau shows SN to the north of 26°N and nearly EW to the south of 26°N. This difference is closely related to the tearing of the subducted Indian slab. The slab tearing shows an abrupt change of the Indian slab subduction angle on the comprehensive geophysical profiles, and the concentrated exposure of picrite, lamprophyre, adakite and leucogranite on the surface. This new model is obviously different from the previous lithosphere delamination and convective thinning. [ABSTRACT FROM AUTHOR]

The study on continental collision process will shed light on plate tectonics within continent. However, there are some problems about the timing of the initial collision, such as the division about collisional phases and the dynamics of collisional metallogenesis. Comparing Zagros and Himalayan orogens in terms of their deformation, magmatism, and metallogenesis, it is noted that there is a time lag between intense collisional related shorting and initial collision. In the meanwhile, arc-like magmatic activity can also occur within collisional continental zone. It is suggested that the lag time between tectonic-magmatic activities and initiation of continental collision reflects the effects of a collision process involving the "soft" collision. Thus the collision processes can be divided into three phases, including soft collision, hard collision, and post collision. Among them, the soft collision phase is characterized by low-rate contractional deformation and magmatism related to sub ducted oceanic slab. In contrast, high-rate contractional deformation and magmatism related to subduction of continental lithosphere occur during the hard collision phase. There are lots of extensional structures during post collision phase, and magmatic activity of this phase is mainly induced by delamination, breakoff and tearing of the continental lithosphere. The hydrothermal Pb-Zn ore deposits occur in the fold and thrust belt during soft and hard collision phases. The porphyry Cu deposits are controlled by large strike-slip faults during hard and post collision phases, whereas the detachment-faultrelated polymetallic deposits form related to crustal extension during post collision phase. The juvenile crust form during the early subduction phase and subsequent collisional phase, and supply metal for ore-forming system within continental collision zones [ABSTRACT FROM AUTHOR]

Tianshan orogen, which is located in the southwestern part of the Central Asian orogenic belt (CAOB), is a window to explore the accretionary orogenic process of the CAOB. The northwest Tianshan orogen, which is the joint of Yili block and Junggar block, preserves the important geological information of the evolution between them. Especially, the Devonian exposed in Biezhentao Mountain on the northern margin of Yili block is an important carrier for recording the evolution of the northwest Tianshan in the early Late Paleozoic. Detrital zircon LAICP- MS U-Pb dating of sandstone from Hanjiga Formation shows that the ages of detrital zircons range from 500 Ma to 370 Ma, and can be divided into two periods: the main period peak value is 386 Ma, followed by 490 Ma. According to the petrographic characteristics, ages and trace elements of zircon, the provenance of sandstone is mainly intermediate-acid magmatic rock of the early Late Paleozoic and intermediate-basic magmatic rock of the early-middle Early Paleozoic. It is inferred that the sedimentary age of Hanjiga Formation is late Middle Devonian and formed in the forearc basin environment. It is also indicated that the detrital materials of the studied sandstone are mainly derived from the Paleozoic magmatic arc in the northern margin of Yili block, which belongs to the near-source sediments. Meanwhile, it is suggested that the northern margin of Yili block is an active continental margin due to the southward subduction of J unggar ocean in the early Late Paleozoic. [ABSTRACT FROM AUTHOR]

The Yining Block is an important part of the West Tianshan orogenic belt. There are many Late Paleozoic volcano-magmatic rocks and sedimentary formations exposed on this block, which is of great significance to decipher its formation and evolution. The Yining Block can be divided into two tectonic units, namely the south and north, bounded by Wusun mountain-Taled fault in EW direction at the central part of the block. They are significantly different in basement construction, composition and age of magmatic rocks, geochemical characteristics, basin formation and tectonic evolution. The south tectonic belt is composed of Dahala-Kalajun island arc zone and Atengtao back-arc extensional basin from Late Devonian to early Early Carboniferous, with the trench being located in the south of the island arc zone (near the southern margin of Nalati fault); the north tectonic belt consists of Awulale superimposed island arc zone, Tekes-Xinyuan fore-arc basin, Qingshuihe-Subutai back-arc basin and fan delta in the middle and late Early Carboniferous. On the basis of resorting and summarizing the latest division scheme of Yining Block, a new understanding of the formation and evolution of Yining Block, namely two collages and three-stage evolution on the two tectonic belts, is put forward for the first time. The detailed processes include: 1) from Late Devonian to early Early Carboniferous, the initial arc-basin system is primarily formed in the south tectonic belt; 2 during the middle and late Early Carboniferous, the trench-arc- basin system in the north tectonic belt is generated and superimposed by the other belt; 3 in the early Late Carboniferous, the initial south tectonic belt and the accretionary north tectonic belt are collaged and sutured, completing the collision and accretion of this block. These processes result in the formation of the unified Yining Block. [ABSTRACT FROM AUTHOR]

The metallogenic belt is a geological unit for possessing potential of ore resources. The metallogenic system mainly focuses on the overall characteristics of mineralization from the aspects of metallogenic elements and processes, including deposit assembly, metallogenic series and their original link. The metallogenic system is an important evidence for dividing metallogenic belt and summarizing metallogenic regularity. East Tianshan orogenic belt, which is sandwiched between Tuha Basin and Tarim block, may be divided into four metallogenic belts in terms of spatial distribution, including Dananhu-Tousuquan Cu-Au-polymetallic metallogenic belt, Kanggurtag-Huangshan Au-Cu-Ni metallogenic belt, Aqishan-Yamansu Fe-Cu-polymetallic metallogenic belt and Caixiashan-Jiyuan Pb-Zn-Ag-polymetallic metallogenic belt. The temporal evolution of East Tianshan orogenic belt is distinctly characterized by multi-stage and multiple metallogenic system, including ① Middle-Late Proterozoic extension continental margin, where there occurs a metallogenic system of sedimentation Pb-Zn-Ag deposits; ② Ordovician-Carboniferous active continental margin, where there occurs a metallogenic system of VMS Cu-Zn deposits and porphyry Cu deposits; ③ Carboniferous island arc, where there occurs a metallogenic system of volcanic Fe-Cu deposits; ④ Late Carboniferous-Early Permian post-collision orogeny and superimposition of mantle plume, where there occurs a metallogenic system of magmatic Cu-Ni deposits and a metallogenic system of Au deposits related to ductile shear processes. [ABSTRACT FROM AUTHOR]

BACKGROUND: The Songlinkou pluton is located in the eastern margin of the Songpan - Ganzi orogenic belt, which is adjacent to the pegmatite - type lithium deposit of Jiajika. OBJECTIVES: In order to explore the similarities and differences between Songlinkou pluton and Jiajika mineralizing intrusive rocks, and to study geological conditions of mineralization and material source of the pluton. METHODS: Geochronology research by LA - ICP - MS zircon U - Pb dating, Lu - Hf isotope study of zircon by MC - ICP MS, the rare earth and trace elements were determined by ICP - MS. RESULTS: The Songlinkou pluton is rich in diorite enclaves, which contents of SiO2 are 56. 56% -68. 99%, total alkali are 3. 78% -6. 82%, K2 O/Na2 O is 1. 02 -1. 93, Rittmann indexes are 1. 01 -1. 93. The rock has relative high Ml values( Ml =46. 73 -61. 27), which has the characteristics of enrichment of light rare earths, the LREE/HREE = 2. 67 - 8. 31, LaN/YbN = 2. 11 - 9. 74, and all samples have strong Eu negative anomaly. It is rich in LILE, but Ta, Nb, P, Ti are depleted of the pluton. The zircon U - Pb results of the granodiorite and monzogranite are 212. 6 ± 1. 0Ma ( MSWD = 0. 55) and 222. 4 ± 1. 1 Ma ( MSWD = 0. 39). The eHf( t) of zircon Lu - Hf isotope of monzogranite is -9. 09 to -6. 86,and TcDM. is between 1524. 9 Ma and 1666 Ma. CONCLUSIONS: The Songliankou pluton belongs to high potassium Cale - alkaline I - type granite, which is the partial melting of the middle Proterozoic Yangtze craton basement and mixed with enrichment of upper mantle material. The Jiajika S - type granite is formed by partial melting of the upper crust, and is different from Songliankou pluton in terms of material sources, magmatic evolution and mineralization tectonic conditions. That may be the main reason why the Songlinkou pluton does not have lithium rare metal mineralization [ABSTRACT FROM AUTHOR]

Yanbian area in Jilin, located at the eastern segment of the southern Xing-Meng orogenic belt, is an overlapped and transformed area between the paleo-Asian ocean and paleo-Pacific ocean tectonic domains. In order to confirm the emplaced age and discuss the petrogenesis and tectonic setting of Shasongdizi gabbros in Belong area of Yanbian, Jilin, the petrography, zircon U-Pb geochronology, Hf isotopic data and geochemistry of the gab bros were analyzed. T he results show that the em placed age of Shasongdingzi gab bro is in late Early Jurassic with the weighted mean age of (175. 6±1. l)Ma; gabbros are characterized by the low Si02 contents and high Al2O3 contents, while the samples have high Cr, Ni, V, Co, Sc contents and Mg# values; meanwhile, the ratios of Zr/ Hf and Ba/ Rb are similar to the ones of mantle igneous rocks, the ratios of Nb/ U are similar to the ones of continental crust, indicating that the continental contamination occurs during evolution; gabbros have low total REE contents and positive Eu anomaly; all the samples are slightly enriched in LREE and enriched in LILE such as Cs, K, Sr, and depleted in HFSE such as Nb and Ta. he geochemical features suggest that the gabbros have subduction-reformed lithospheric mantle-derived primary magma contaminated by upper crustal materials during evolution. The gabbros have depleted Hf isotopic compositions with εHI(t) of 2. 5-7. 0. In summary, the primary magma of gab bros may be from the depleted mantle, which is metasomatized by fluids from subducted oceanic slab and is contaminated by the crustal materials. Furthermore, the Shasongdingzi gabbros form in an active continental margin during the subduction of paleo-Pacific. [ABSTRACT FROM AUTHOR]

Objectives: The Badong-Zigui Basin is located in the west of the Three Gorges area, and it is surrounded by four different tectonic units: With the Xuefengshan thick-soil tectonic belt on the south, the Qinling orogenic belt on the north, the Huangling anticline on the east, and the eastern extension of the Sichuan Basin in the west. The Badong-Zigui basin is a north-south syncline structure, the sediments in the basin are dominated by Late Triassic-Late Turassic argillaceous rocks, and the special tectonic setting causes strong tectonic activities in the basin. Methods: Using a three-dimensional gravity inversion algorithm based on Lagrangian multiplier constraints, the local Bouguer gravity anomaly in Badong-Zigui area is inverted, and the underground three-dimensional density structure of Badong-Zigui and adjacent areas is obtained. Results: The inversion results show that the Zigui Basin is a low-density area compared with the surrounding area. The sedimentation thickness in the east is deeper than that in the west, and the sediment density is lower than that in the west. The small and medium earthquakes in the area are basically 4-12 km underground. Conclusions: The north-south and north-east ancient water flows in the northern edge of the Zigui Basin successively provide sources for the sedimentation and filling of the basin, forming a structure with lower material density and deeper deposits in the eastern part of the basin; low-density materials in the east are transported and accumulated to the west in the basin. At the same time, it is squeezed by the eastward extension of the Sichuan Basin, and it is speculated that there is a tendency of east-west movement and compression in the basin. [ABSTRACT FROM AUTHOR]

As an important part of arc magmatic rocks in East Kunlun, Dagele granites are of great significance to the interpretation of the evolution of Paleo-Tethys. In order to study its petrogenesis and tectonic setting, the petrology, zircon U-Pb geochronology and petrogeochemistry of granites exposed in Dalage area, the eastern margin of East Kunlun orogenic belt were studied in detail. The results show that Dagele plutons are composed of grey medium- to fine-grained granites, and some dark diorite enclaves; LA-ICP-MS Zircon U-Pb ages of granite and diorite enclave are (261. 0 + 2. 8) Ma and (261. 6 + 1. 6)Ma, respectively; granites are medium-high K calc-alkaline and metaluminous to weak peraluminous series, and belong to I-type granites; the characteristics of REE show that LREEs are relatively abundant, and HREEs are relatively depleted; the characteristics of trace elements show that the granites are rich in Rb, Th, U, etc. , and poor in Nb, Ta, etc. , with low Mg* and ratio of Nb/Ta; diorite enclaves are featured by medium K calc-alkaline, and rich in Fe, Mg, Ca, Ti, etc. , with high Mg*. Petrogenesis studies show that granites are the production of partial melting of amphibolite in the continental lower crust, hut diorite enclave is the production of rapid condensation of mafic magma injected into granites. Combined with regional data, it is suggested that Dagele granites form in the continental arc environment related to the northward subduction of Buqingshan-Anemaqen ocean, which further indicates that Paleo-Tethys ocean has subducted northward under North East Kunlun terrane in Late Permian. [ABSTRACT FROM AUTHOR]

Based on the analysis results of thin sections, cathodoluminescence of quartz and heavy mineral assemblages, combined with sedimentary structures and seismic reflection characteristics, the provenance direction, parent rocks and evolution characteristics of Upper Triassic-Middle Jurassic in the eastern Kuqa depression of Tarim Basin were studied. The results show that the provenance of Upper Triassic-Middle Jurassic in the eastern Kuqa depression of Tarim Basin is mainly from South Tianshan orogenic belt in the north, and the parent rocks are mainly magmatic and metamorphic with a few sedimentary. Among them, there is a higher content of terrigenous clastic lithic and quartz without luminescence in the sandstone of Taliqike Formation, and the heavy mineral assemblages are characterized by higher contents of zircon, leucosphenite and magnetite, and lower contents of garnet, indicating that the parent rocks may be early deposition of Upper Ordovician-Upper Triassic; the contents of magmatic rock lithic in the sandstone of Ahe Formation and Yangxia Formation increase, the heavy minerals are characterized by higher contents of garnet, and quartz mainly gives off blue-purple and tan light under the condition of cathodoluminescence, indicating that the parent rocks of Ahe Formation and Yangxia Formation mainly come from Permian and its underlied sediments; the contents of metamorphic rock lithic and quartz with tan luminescent in the sandstone of Kezilenu'er Formation and Qiakemake Formation increase obviously, and the content of garnet is extremely high, indicating that the influence of metamorphic parent rock is enhanced. The evolution of parent rocks in the provenance area of Late Triassic-Middle Jurassic has obvious regularity. The parent rocks are mainly sedimentary in Late Triassic, and the contents of magmatic parent rocks increase in Early Jurassic, and finally, it is characterized by metamorphic parent rocks in Middle Jurassic. In Late Triassic, the South Tianshan orogenic belt is greatly uplifted in the eastern Kuqa depression, as a result, a large number of metamorphic parent rocks are involved in the orogenic belt and denuded; in Early-Middle Jurassic, the tectonic activity in the middle section of South Tianshan orogenic belt is characterized by east and west sections, the sandstone in the eastern region firstly has high content of garnet in Early Jurassic, while the sandstone in the western region does not appear garnet abundance until Middle Jurassic. It shows that Hula and E'erbin mountains in the middle section of South Tianshan orogenic belt are uplifted and denuded strongly in Early Jurassic, but Halke mountain is uplifted consumingly in Middle Jurassic. [ABSTRACT FROM AUTHOR]

An integrated study of mineralogy and in-situ LA-ICP-MS trace element analysis was conducted on rutiles from Yukahe ultrahigh-pressure metamorphic(UHPM)phengite eclogite and garnet amphibole albitite in the northern Qaidam Basin, NW China. The results show that rutiles from these two UHPM rocks have high Si contents, and during the metamorphic evolution of phengite eclogite, Si contents of rutile grains grown in different metamorphic stages as well as the core and rim parts of a single rutile grain change regularly with metamorphic pressure. The Si contents in prograde rutiles, which occur as inclusions in garnet, omphacite and phengite core, increase gradually from core((342-360)×10-6)to rim; the Si contents in peak rutiles, which coexist with garnet, omphacite and phengite in matrix or occur as inclusions in garnet mantle and rim, have the highest Si contents with an average value of 952×10-6 and a maximum value of 2 397×10-6; the Si contents in retrograde rutiles, which coexist symplectite with amphibole+plagioclase formed by omphacite decomposition or occur in phengite+quartz veins of eclogite, decrease gradually from core towards rim(the average Si content of symplectite is 726×10-6, and that of microveins is 674×10-6). Rutiles in garnet amphibole albitite mainly occur as inclusions in phengite, garnet, amphibole and albite, and the rutiles in different occurrences have obviously higher Si contents(1 808×10-6 on average)than those from phengite eclogite(762×10-6 on average). In which, the rutiles included in phengite have Si contents of(1 018-2 741)×10-6 with an average value of 1 924×10-6, whereas the rutiles hosted by albite have variable Si contents of(685-3 910)×10-6 with an average value of 1 761×10-6. Combined with the occurrences, metamorphic evolutions and whole rock compositons of phengite eclogite and garnet amphibole albitite as well as the previous results on Si-bearing rutiles of ultrahigh-pressure eclogites in Dabie-Sulu orogenic belt, it is proposed that Si contents of rutiles from UHPM rocks are positively correlated with metamorphic pressure, and the rutiles with high-Si content(>500×10-6)may be a fingerprint for eclogite experiencing ultrahigh-pressure metamorphism; the whole rock SiO2 and TiO2 contents affect the Si contents of rutiles under the same ultrahigh metamorphic pressure, and the Si contents of rutiles increase as whole SiO2 rises and TiO2 decreases. [ABSTRACT FROM AUTHOR]

West Qinling orogenic belt is characterized by large amounts of Indosinian high-K calc-alkali granites, and the age and genesis of granites are essential to understand the tectonic evolution and magma activity in West Qinling. The detailed field geological investigation, petrography observation, LA-ICP-MS zircon U-Pb ages and geochemistry of whole rock for Sarijia intrusion in Duowa area of West Qinling were studied with the aim of ascertaining the age, genetic type and geodynamic background of the intrusion. The results show that Sarijia intrusion is composed of dacite porphyrite, granite porphyrite and slight quartz diorite; granite porphyrite has a LA-ICP-MS zircon U-Pb age of(238.2±2.6)Ma(MSWD is 1.7); Sarijia intrusion belongs to peraluminous and high-K calc-alkali series, which is enriched in large ion lithophile elements(Th, Rb and K)and light rare earth elements(LREEs), and depleted in high field strength elements(Nb, Ta and Ti, etc.), indicating that the magmatic source is characterized by crust-mantle mixing; the characteristics of major and trace elements show that dacite porphyrite belongs to I-type granite and forms in the ocean-continent subduction-related island arc enviroment, while granite porphyrite belongs to S-type granite and forms in the continental collision setting. Therefore, it is proposed that Sarijia intrusion is emplaced at Late Triassic when the tectonic setting is transformed from ocean-continent subduction-related environment to continental collision setting. [ABSTRACT FROM AUTHOR]

别也萨麻斯矿床是目前新发现的分布在新疆北阿尔泰以Li矿化为主的花岗伟晶岩型稀有金属矿床,具有独特性和代表性。矿区发育Li-Nb-Ta矿化和Nb-Ta矿化两类伟晶岩,二云母二长花岗岩是含矿伟晶岩脉群的直接围岩。在系统的野外地质特征调查(包括野外露头和钻孔岩芯赋矿岩系、矿化特征、蚀变类型等的详细观察)基础上,对含矿伟晶岩和二云母二长花岗岩开展了LA-ICP-MS锆石U-Pb定年和原位Hf同位素研究。获得锆石206Pb/238U加权平均年龄分别为(151.0±1.8)Ma和(449.0±4.2)Ma,含矿伟晶岩形成于晚侏罗世,二云母二长花岗岩则形成于晚奥陶世。含矿伟晶岩和二云母二长花岗岩的εHf(t)值分别为0.62～1.30和1.35～6.07,二阶段Hf模式年龄为1 161～1 118 Ma和1 345～1 037 Ma。含矿伟晶岩的εHf(t)值较花岗岩小得多,二阶段Hf模式年龄与形成年龄的差值较花岗岩大得多,表明两者是阿尔泰造山带在不同演化阶段下的产物。悬殊的年龄差、不同的大地构造背景与不同的形成物源表明别也萨麻斯稀有金属矿床含矿伟晶岩与二云母二长花岗岩在成因上并无联系,近矿花岗岩围岩并非含矿伟晶岩脉的真正母体。 [ABSTRACT FROM AUTHOR]

Hunan province is rich in endogenic minerals, which are formed mainly in three mineralization events such as Caledonian(mainly Silurian), Late Indosinian(Late Triassic)and Middle-Late Yanshanian(Late Jurassic-Early Cretaceous). Based on regional mineral data and achievements of geotectonic, diagenetic and metallogenic ages, the tectonic framework controlling characteristics and dynamic mechanisms of the three endogenous mineralization events were discussed. (1)In Caledonian, controlled by the expanding of Caledonian movement and deep lithosphere structural differences, Hunan province could be divided into three tectonic belts with different mineralization characteristics from southeast to northwest. In the central-southeastern Hunan tectono-magmatic belt(I), there occurred post-collisional granitic magmatism, which caused W and fluorite deposits locally; in Xuefeng thrust-fault zone(II1)of the eastern Xuefeng tectonic belt(II), there occurred Au and Au-Sb deposits related mainly with structural activation; in Wuling gentle fold zone(II2)of the western Xuefeng tectonic belt(III)and in the northwestern Hunan tectonic lifting belt(I), there occurred Hg-Pb-Zn deposits related with Cambrian synsedimentary faults, extension after Caledonian movement and hydrothermal activity. (1)In Late Indosinian, controlled by deep lithosphere structural differences, Hunan province could be divided into three tectonic belts from southeast to northwest. In the central-southeastern Hunan tectono-magmatic belt(I), there occurred larger-scale post-collisional granitic magmatism for the weakening of stress, which caused W-Sn-Pb-Zb-polymetallic deposits in the southeast and Sb-Au-W-polymetallic deposits in the northwest; Xuefeng tectonic belt(II)maybe has no endogenous hydrothermal mineralization; in the northwestern Hunan fold belt(III), there occurred small vein type of Pb-Zn deposits. (3)In Middle-Late Yanshanian, Hunan province could be divided into three tectonic belts from southeast to northwest. In the central-southeastern Hunan tectono-magmatic belt(I), there occurred larger-scale granitic magmatism due to deep tectonisms such as lithospheric delamination, upwelling of asthenosphere mantle, temperature rising and stress weakening after intracontinental collision, and subduction plate collapse, and accordingly enormous norferrous and Au deposits were formed; in the western Xuefeng tectonic belt(II), there occurred weak mineralization with Au, Hg deposits locally; in the northwestern Hunan fold belt(III), there occurred a few low temperature hydrothermal filling fluorite and As deposits. [ABSTRACT FROM AUTHOR]

The 2015 Nepal Mw 7.9 earthquake occurred in the central segment of the Himalayan collision zone where the rigid Indian plate is underthrusted beneath the Tibetan Plateau. Refining the coseismic slip distribution and afterslip of the earthquake has great significance for better understanding the seismogenic mechanism in Himalaya orogenic belt. We adopted the angular dislocation elements to construct the rampflat- ramp-flat fault geometry of the main Himalayan thrust. In combining with GPS and InSAR data, we inverted the coseismic slip distribution and afterslip of the Nepal earthquake. The result shows that the mainshock is dominated by thrust slip with minor right-lateral strike-slip. The maximum slip of the mainshock is up to 7.8 m at a depth of 15 km, near to the intersection between the upper flat and mid-crust ramp. The total geodetic moment based on our preferred slip model is M0=8.39×1020 N·m, corresponding to an Mw of 7.93 assuming a shear modulus of 30 GPa. The released moment is mainly confined to the depth of 15— 25 km, in which nearly 50% of the released moment locates at the ramp of upper crust. The maximum slip could be underestimated if we ignore the mid-crust ramp. The inferred afterslip primarily concentrates on the downdip of the coseismic rupture. The afterslip is characterized by pure thrust slip with the maximal amplitude of 0.5 m. The total released moment by the afterslip is estimated to be 1.02×1020 N·m, equiva⁃ lent to an Mw 7.3 earthquake, approximately 12% of the coseismic moment. The coseismic static Coulomb stress change suggests that the southern part to the rupture zone of the Nepal earthquake with a width of about 60 km is largely promoted by the 2015 Nepal earthquake. Considering the fact that this area is strongly locked during the interseismic period, the near-term seismic hazard in this area deserves special attention. [ABSTRACT FROM AUTHOR]

Middle Jurassic Zhiluo Formation in the southwestern Ordos Basin is a new potential exploration target with low degree of exploration. Rased on outcrop and core observation, interpretation of logging data and thin sections identification, the paleocurrent and paleogeomorphology were reconstructed to reveal the distribution of paleo drainage system; based on the logging interpretation of more than 500 boreholes, combined the constraint of paleogeomorphology and paleo drainage, the macroscopic dispersion system of sand bod y and the distribution of sedimentary faciès were proposed. The results show that the source of Zhiluo Formation in the southwestern Ordos Basin is mainly from West Qinling orogenic belt in the southwest the supply of sand is abundant in early, and the sedimentary environment is braided river braided river delta, which builds grey thick sandstone intercalated with mudsione; then the supply of source changes to fine grains dominated, and the sedimentary environment turns into meandering river delta characterized by the development of purple mudsione with sandstone interbed; sandstone reservoir of Zhiluo Formation is dominated by primary iniergranular pores and dissolution pores. and the porosity is 0.87%-31. 20% with the average of 16. 34%, the permeability is (0.13-53.70) × 10-3 μm2 with the average of 17. 83×10-3 μm2 . the lowest porosity limit of effective reservoir is 15% in the early deposition of Zhiluo Formation, the paleogeomorphology not only controls the development and distribution of sandbody. but also influences the advantageous position for the development of sandbody and the direction of hydrocarbon migration subsequently; potential reservoir targets include three types of hydrocarbon accumulation models related with paleogeomorphology that is highlands in upstream curved slop toe in midstream and interriver mound in downstream. [ABSTRACT FROM AUTHOR]

The provenance characteristics of Yanghugou Formation in the western margin of Ordos Basin is particularly important for natural gas exploration. Through the studies on clastic components, lithic components, heavy mineral combination and quartz cathodoluminescence(CL)of sandstones, it is believed that Yanghugou Formation is controlled by the provenances in the north, southwest and south of the study area, which meet at Wuzhong-Majiatan area in the middle of the study area. Through the analysis on light and heavy mineral combination, Dickinson triangle diagram of debris components of sandstones, and rare earth element(REE)characteristics of mudstones, it is believed that the source rocks of Yanghugou Formation in the study area are dominated by continental crust rocks. The north sandstone provenance is a recyclic orogenic belt, the chondrite-normalized REE pattern of mudstone is similar to that of Alashan paleocontinental metamorphic rock; the southwest and south provenances are stable land masses and recyclic orogenic belts, the chondrite-normalized REE pattern of mudstone is similar to that of the shallow metamorphic rocks in Qilian-North Qinling orogenic belt. In conclusion, the parent rock in the north of the study area is mainly a shallow metamorphic rock with a small volcanic rock in Alashan paleocontinent, and the parent rocks in the southwest and south are mainly the medium-shallow metamorphic rocks in Qilian-North Qinling orogenic belt, followed by carbonate and volcanic rocks. [ABSTRACT FROM AUTHOR]

Guanshan area is located in the junction of North Qinling and North Qilian orogenic belt, and it has a lot of controversy about the genesis of Guanshan pluton at present. The zircon U-Pb dating results show that the monzogranite of Guanshan pluton is formed in(236.3±4.0)Ma(the number of sample is 6, MSWD is 2.6). Late Triassic Guanshan monzogranite in North Qinling displays the characteristics of high Si(the content of SiO2 is more than 69%)and alkali-rich(the content of K2O is more than 3.84%, that of Na2O is more than 4.18%), Mg# is on the high side(50.4-51.0), LREE is enriched, HREE is depleted and flat, Eu has a non-obvious negative anomaly(0.75-0.82). The rock is enriched in Sr, Rb, Ba, and depleted in Y, Yb and other elements, the ratio of Sr/Y is 37.5-60.7, indicating that the rock has the propertieswith adakite. Zircon Lu-Hf isotope displays that 5 grains of the monzogranite have negative εHf(t)(-21.59--4.49)with corresponding two-stage Hf pattern ages of 1 538-2 622 Ma, and 1 grain has positive εHf(t)(0.19)with two-stage Hf pattern age of 1 245 Ma, indicating that Guanshan pluton is derived from the melting of Neoproterzoic crustal material. The rock has high SiO2 and Al2O3 contents, low MgO, Cr and Ni contents, indicating the pluton derives from the melting of crustal material. Compared with the standard value of the crust, the higher Mg# indicates the addition of the mantle component in the source of Guanshan pluton. The petrography, geochemistry, isotopic characteristics and regional geological data comprehensively show that the monzogranite of Guanshan pluton is formed under the tectonic setting of collisional compression, and the lower crust is thickened, dehydrated and melted with the addition of mantle components. [ABSTRACT FROM AUTHOR]

The Dazhuba-Huijun Oblique syncline is located at the center of the Micangshan-Hannan paleo-uplift with structural coupling between the Sichuan Basin and the Qinling Orogenic Belt. In order to study the adsorption characteristic of the Niutitang Formation shale in this region, the isothermal adsorption experiments at different temperatures were combined with TOC, Ro%, XRD, and pore structure analysis. The absorption thermodynamic parameters of the samples were calculated according to the three-parameter excess sorption function combined with the principle of thermodynamic adsorption, and the main factors affecting the adsorption of shale were analyzed. The equal adsorption heat of the samples is between 5.3 and 22.2 kJ/mol, and the standard adsorption entropy are-48.8 to-98.8 J/ (mol·K) . It is influenced by the degree of thermal evolution in the study area, and the thermodynamic parameters show a certain adsorption characteristic of type II and Type III kerogen. The pore BET specific surface area has two peaks in the range of pore diameter less than 2 nm, providing the main sites for methane adsorption. When the adsorption pressure is lowerthan 2.8 MPa, the adsorption of organic matter dominated the methane adsorption of shale. While the adsorption pressure is higher than 2.8 MPa, the clay mineral and organic matter determine the methane adsorption of shale. [ABSTRACT FROM AUTHOR]

Susong metamorphic complex is located at the southernmost end of Dabie orogenic belt, and is one of the important components of the orogenic belt. Due to the relatively low degree of metamorphism and relatively little information of metamorphic evolution, the construction of metamorphic P-T path has challenged geologists for many years, which restricts the full understanding of the formation mechanism of Dabie orogenic belt. The detailed petrographic, mineralogical and thermodynamic evaluation of garnet-plagioclase amphibolite, which was a typical rock from Susong metamorphic complex, were carried out. the results show that this kind of rocks has four metamorphic stage mineral assemblages including Ts+Ep+Qz+Rt, Grt+Pl+Ts+Qz+Ep+Rt, Pl+Ts+Qz+Mag and mainly Chl+Qz, and the corresponding temperatures and pressures are 591 ℃-620 ℃, 606 ℃-636 ℃, 600 ℃-619 ℃ and 400 ℃-500 ℃, and 0.48-0.56 GPa, 1.01-1.12 GPa, 0.79-0.91 GPa and 0.1-0.3 GPa, showing a metamorphic P-T pattern of near-isothermal pressure lift→near-isothermal pressure reduction→temperature reduction and depressurization. The establishment of this P-T path indicates that Susong metamorphic complex experiences rapid subduction and exhumation in the early stage, and slow uplift in the late stage, suggesting that Susong metamorphic complex, as the leading edge block of Yangtze plate, subducts rapidly under the dragging action of the oceanic plate, returns rapidly due to the buoyancy of the plate fragments, stays at the upper crustal level for a long time, and then rises slowly to the surface. [ABSTRACT FROM AUTHOR]

The Neoproterozoic mafic dykes are widespread in Jiangnan orogen. The study on genesis and tectonic setting has significant implications for the tectonic process of Jiangnan orogen and Neoproterozoic tectonic evolution in South China plate. A systematic geochemical study on Neoproterozoic mafic dykes from Maotan area of western Zhejiang at the northeastern part of Jiangnan orogen was carried out. The results show that mafic dykes are mainly diabases and a small amount of gabbros; they are tholeiitic series according to petrography and geochemical characteristics; the REE characteristics show the transition from tholeiitic series to high-alumina series; the negative Nb, Ta, Ti anomalies on primitive mantle-normalized trace element spider diagram show the characteristics of island arc tholeiite, but the mafic dyke samples mainly fall in tectonic environment areas of ocean island, mid-ocean ridge and intraplate basalt on the diagrams of MgO-FeO*-Al2O3, Ti/100-Zr-3Y, TiO2-FeOT/MgO, Zr/Y-Zr, Ti-Zr, Zr/4-2Nb-Y and Th/Yb-Ta/Yb, etc.; the mafic dykes are formed on extensional tectonic setting, mainly on the intraplate rift environment, and suffers crustal contamination during ascending emplacement to varying degrees; all the w(Th)/w(Ta) and w(La)/w(Yb) of the mafic dykes are relatively low; combined with the tectonic environment discrimination diagrams of the rocks and their tholeiitic properties, the mafic dykes show the mantle plume characteristic in geochemistry. The above characteristics indicate that the mafic dykes are formed by the intrusion of the basic magma along the regional fractures, caused by the rifting of crust; the magma is generated by partial melting of lower mantle during the asthenosphere upwelling; it is related to Neoproterozoic plume event and the breakup of Rodinia supercontinent. [ABSTRACT FROM AUTHOR]

The Ni-Cu sulfide deposits in orogenic belts are very important in China. Nickel metal reserves of the Ni-Cu sulfide deposits discovered in orogenic belts, China, including a series of deposits in the southern margin of Central Asian orogenic belt and the large Xiarihamu Ni-Co deposit in East Kunlun orogenic belt, are more than 300×104 t. These discoveries make China having the most abundant magmatic sulfide deposits in orogenic belts over the world. However, some important issues on the formation of such deposits have not been well understood. For instance, what results in the formation of those large and super-large Ni-Cu sulfide deposits in the orogenic belts? What are the features of the related magmatism? When the magmatism occurs during tectonic evolution of the orogenic belts? What is the mechanism leading the extensive mafic magmatism? The above issues predominantly based on the recent studies of Huangshan-Jing’erquan Ni-Cu sulfide deposit belt as well as Permian regional strike-slip structure in northern Tianshan, Xinjiang were focused on. The results show that the collision between Junggar-Kazakhstan block and Tarim block along with regional dextral strike-slip structure in Permian results in break-off of the subduction oceanic slab and upwelling of the asthenosphere; the upwelling of the asthenosphere causes extensive melting of itself, and the metasomatized wedge mantle produces mafic magma; the strike-slip faults provide the pass way for the ascending mafic magmas and create spaces for the magmatic sulfide mineralized intrusions in the crust of Huangshan-Jing’erquan Ni-Cu sulfide deposit belt. [ABSTRACT FROM AUTHOR]