Molecular Biomarker Characteristics of the Linxi Formation Source Rocks in the Middle-Western Region of Inner Mongolia:New evidence for late-stage tectonic evolution of the Paleo-Asian Ocean

Objective Two important geological issues have long been controversial in the Xing-Meng area of North China. The first concerns the final closure of Paleo-Asian Ocean in Xing-Meng area, and the other concerns the folding and lifting of the Xing-Meng Trough. The focus of thses issues is the Late Permian sedimentary environment, which is generally considered to be either an exclusively continental environment or from the closed inland sea environment in the Early to Middle stage to continental lacustrine environment in the late stage. In recent years, we have successively discovered abundant typical marine fossils （e.g., bryozoans and calcareous algae） in the Upper Permian thick limestone layer from Linxi County and Ar Horqin Banner in eastern region of Inner Mongolia and Jiutain County in Jilin Province. These significant findings have attracted the attention from fellow academics.

Petrology, Geochronology and Geochemistry of the Xar Moron River Ophiolite: Implications for the Tectonic Evolution of the Paleo-Asian Ocean

As the largest accretionary orogen, the crustal tectonic framework and evolution of the Central Asian Orogenic Belt(CAOB) have always been one of the hot topics among geologists(Seng?r et al., 1993, 1996;Jahn et al., 2000 a;Badarch et al., 2002;Windley et al., 2007;Li et al., 2009). The formation of the main part of the crust in the CAOB involved continuous lateral accretion of island arcs and accretionary complexes along the margins of the Siberian, Sino-Korean and Tarim paleocontinents and the final collision between these continental margins because of the subduction of the Paleo-Asian Ocean plate since Mesoproterozoic. The ophiolites, which represent the fragments of ancient oceanic lithosphere, are the direct evidence for the study of the evolution of orogenic belts. Based on field geological survey, the mantle peridotite(serpentinite), gabbro, basalt and radiolarian bedded chert, which were deemed as the "ophiolite trinity", were identified as isolated blocks in the matrix of pelitic siltstone and silty mudstone in the Kedanshan, Xingshuwa and Jiujingzi areas along the Xar Monron River in southeast Inner Mongolia of China. Besides, there were plenty of other exotic blocks, such as limestone and sandstone, in the matrix. Both of the matrix and blocks underwent strong foliated deformation. All of these rocks above constitute a tectonic mélange. Zircon U-Pb dating for the gabbro blocks in the Xingshuwa and Jiujingzi ophiolites reveals that they were formed in early Permian(275-280 Ma). The ages of the gabbros, together with the middle Permian radiolaria fossils in the chert reported by Wang and Fan(1997), indicate that the oceanic basin was not closed in early-middle Permian. The geochemical compositions of the basaltic blocks distributed in different locations in the Xingshuwa tectonic mélange display different genetic types of normal mid-ocean ridge basalt(N-MORB), enriched mid-ocean ridge basalts(E-MORB), oceanic island basalt(OIB), island arc basalt and continental marginal arc basalt, which indicates what they represented is a complex oceanic basin. Combining with the studies on regional magmatism, strata and structure data, it is suggested that the Xar Moron River Ophiolite belt represented the final suture zone of the Paleo-Asian Ocean in the southeast Inner Mongolia, and the ocean did not close before late Permian.

Petrologic perspectives on tectonic evolution of a nascent basin(Okinawa Trough) behind Ryukyu Arc: A review

Okinawa Trough is a back-arc, initial marginal sea basin, located behind the Ryukyu Arc-Trench System. The formation and evolution of the Okinawa Trough is intimately related to the subduction process of the Philippine Sea Plate beneath the Eurasian Plate since the late Miocene. The tectonic evolution of the trough is similar to other active back-arcs, such as the Mariana Trough and southern Lau Basin, all of which are experiencing the initial rifting and subsequent spreading process. This study reviews all petrologic and geochemical data of mafic volcanic lavas from the Okinawa Trough, Ryukyu Arc, and Philippine Sea Plate, combined with geophysical data to indicate the relationship between the subduction sources （input） and arc or back-arc magmas （output） in the Philippine Sea Plate-Ryukyu Arc-Okinawa Trough system （PROS）. The results obtained showed that several components were variably involved in the petrogenesis of the Oki-nawa Trough lavas：sub-continental lithospheric mantle underlying the Eurasian Plate, Indian mid-oceanic ridge basalt （MORB）-type mantle, and Pacific MORB-type mantle. The addition of shallow aqueous fluids and deep hydrous melts from subducted components with the characteristics of Indian MORB-type mantle into the mantle source of lavas variably modifies the primitive mantle wedge beneath the Ryukyu and sub-continental lithospheric mantle （SCLM） beneath the Okinawa Trough. In the northeastern end of the trough and arc, instead of Indian MORB-type mantle, Pacific MORB-type mantle dominates the magma source. Along the strike of the Ryukyu Arc and Okinawa Trough, the systematic variations in trace element ratios and isotopic compositions reflect the first-order effect of variable subduction input on the magma source. In general, petrologic data, combined with geophysical data, imply that the Okinawa Trough is experiencing the＂seafloor spreading＂process in the southwest segment,＂rift propagation＂process in the middle seg-ment, and＂crustal extension＂process in the northeast segment, and a nascent ocean basin occurs in the southwest segment.

Paleozoic tectonic evolution of the eastern Central Asian Orogenic Belt in NE China

The eastern Central Asian Orogenic Belt(CAOB)in NE China is a key area for investigating continental growth.However,the complexity of its Paleozoic geological history has meant that the tectonic development of this belt is not fully understood.NE China is composed of the Erguna and Jiamusi blocks in the northern and eastern parts and the Xing’an and Songliao-Xilinhot accretionary terranes in the central and southern parts.The Erguna and Jiamusi blocks have Precambrian basements with Siberia and Gondwana affinities,respectively.In contrast,the Xing’an and Songliao-Xilinhot accretionary terranes were formed via subduction and collision processes.These blocks and terranes were separated by the Xinlin-Xiguitu,Heilongjiang,Nenjiang,and Solonker oceans from north to south,and these oceans closed during the Cambrian(ca.500 Ma),Late Silurian(ca.420 Ma),early Late Carboniferous(ca.320 Ma),and Late Permian to Middle Triassic(260-240 Ma),respectively,forming the Xinlin-Xiguitu,Mudanjiang-Yilan,Hegenshan-Heihe,Solonker-Linxi,and Changchun-Yanji suture zones.Two oceanic tectonic cycles took place in the eastern Paleo-Asian Ocean(PAO),namely,the Early Paleozoic cycle involving the Xinlin-Xiguitu and Heilongjiang oceans and the late Paleozoic cycle involving the Nenjiang-Solonker oceans.The Paleozoic tectonic pattern of the eastern CAOB generally shows structural features that trend east-west.The timing of accretion and collision events of the eastern CAOB during the Paleozoic youngs progressively from north to south.The branch ocean basins of the eastern PAO closed from west to east in a scissor-like manner.A bi-directional subduction regime dominated during the narrowing and closure process of the eastern PAO,which led to“soft collision”of tectonic units on each side,forming huge accretionary orogenic belts in central Asia.

Tectonic Evolution and Key Geological Issues of the ProtoSouth China Sea

There are numerous controversies surrounding the tectonic properties and evolution of the Proto-South China Sea(PSCS).By combining data from previously published works with our geological and paleontological observations of the South China Sea(SCS),we propose that the PSCS should be analyzed within two separate contexts:its paleogeographic location and the history of its oceanic crust.With respect to its paleogeographic location,the tectonic properties of the PSCS vary widely from the Triassic to the mid-Late Cretaceous.In the Triassic,the Paleo-Tethys and the Paleo-Pacific Oceans were the major causes of tectonic changes in the SCS,while the PCSC may have been a remnant sea residing upon Tethys or Paleo-Pacific oceanic crust.In the Jurassic,the Meso-Tethys and the Paleo-Pacific oceans joined,creating a PSCS back-arc basin consisting of Meso-Tethys and/or Paleo-Pacific oceanic crust.From the Early Cretaceous to the midLate Cretaceous,the Paleo-Pacific Ocean was the main tectonic body affecting the SCS;the PSCS may have been a marginal sea or a back-arc basin with Paleo-Pacific oceanic crust.With respect to its oceanic crust,due to the subduction and retreat of the Paleo-Pacific plate in Southeast Asia at the end of the Late Cretaceous,the SCS probably produced new oceanic crust,which allowed the PSCS to formally emerge.At this time,the PSCS was most likely a combination of a new marginal sea and a remnant sea;its oceanic crust,which eventually subducted and became extinct,consisted of both new oceanic crust and remnant oceanic crust from the Paleo-Pacific Ocean.In the present day,the remnant PSCS oceanic crust is located in the southwestern Nansha Trough.

Zircon U–Pb Geochronology and Petrogenesis of Early–Midlle Permian Arc–Related Volcanic Rocks in Central Jilin: Implications for the Tectonic Evolution of the Eastern Segment of Central Asian Orogenic Belt

This paper presents age and geochemical data of a recently identified Late Paleozoic volcanic sequence in central Jilin Province, with aims to discuss the petrogenesis and to constrain the tectonic evolution of the Central Asian Orogenic Belt in this area. Firstly, the volcanic rocks have zircon U-Pb ages of 290–270 Ma. Secondly, they are characterized by(a) ranging in composition from the low-K tholeiite series to high-K calc-alkaline series;(b) enrichment in light rare earth elements and depletion of heavy rare earth elements, with negative Eu anomalies;and(c) negative Nb, Ta, and Ti anomalies. Finally, the volcanic rocks yield εHf(t) values of +7.1 to +17. These data suggest that the central Jilin volcanic rocks were possibly derived from predominant partial melting of a depleted lithospheric mantle that might have been modified by subducted slab–derived fluids. Combined with previous studies, the Late Paleozoic–Early Mesozoic magmatism in Central Jilin can be divided into two stages:(a) a volcanic arc stage(290–270 Ma) represented by low-K to high–K, tholeiite to calc–alkaline plutons and(b) a syn–collisional stage(260–240 Ma) represented by high-K calc–alkaline I-type granites. Furthermore, the timing and the tectonic setting of the above magmatic rocks show that the arc was probably produced by the northward subduction of the Paleo-Asian Ocean and that the final closure of the Paleo-Asian Ocean occurred prior to the Early Triassic.

Neoproterozoic-Paleozoic Tectonic Evolution of the Northeastern Tarim Block： Constraints from ^40Ar/^39Ar Geochronology in the Kuluketage Area, NW China

Seventeen new ^40Ar/^39Ar analyses reported for ten Tarim Precambrian basement samples from the Kuluketage area, are applied to reconstruct the regional thermo-tectonic history together with previously published data. Eight samples were taken adjacent to the Xingdi and Xinger faults, major structures in the study area, whereas a further two were sampled at some distance from the faults. 4^40Ar/^39Ar data from the latter record rapid cooling following a Neoproterozoic magmatic/metamorphic event and mild Paleozoic thermal disturbance. Paleozoic ^40Ar/^39Ar ages from the study area, as well as from the Central Tianshan and eastern Southern Tianshan suggest two strong deformational periods at ~390 Ma and ~300 Ma. During the older period, argon isotopic systems were reset/disturbed by high temperature related to arc magmatism resulting from subduction of the South Tianshan paleo-oceanic crust, possibly in combination with reactivation of Precambrian faults. The younger period is characterized by widespread late Carboniferous-early Permian intracontinental deformation, which is related to the final amalgamation of the Central Asian Orogenic Belt. Previously published apatite fission track data attest to a long history of post-collisional cooling, which is attributed to continued propagation of deformation within the Central Asian Orogenic Belt.

Zircon U-Pb-Hf isotopic and geochemical characteristics of the Xierzi biotite monzogranite pluton,Linxi,Inner Mongolia and its tectonic implications

The opening, subduction and final closure of the Paleo-Asian Ocean led to the formation of the Central Asian Orogenic Belt. Controversy has long surrounded the timing of final closure of the Paleo-Asian Ocean. Here we present zircon U-Pb ages and petrological, geochemical and in situ Hf isotope data for the Xierzi biotite monzogranite pluton, Linxi, SE Inner Mongolia. U-Pb dating of zircon by LA-ICP-MS yields a middle Permian emplacement age(268.7 ± 2.3 Ma) for the Xierzi pluton that is dominated by biotite monzogranites with high SiO_2(71.2-72.8 wt.%),alkali(Na_2 O + K_2 O =8.05-8.44 wt.%), Al_2 O_3(14.4-15.2 wt.%) and Fe_2 O_3~T relative to low MgO contents, yielding Fe_2 O_3~T/MgO ratios of 2.87-3.44, and plotting within the high-K calc-alkaline field on a SiO_2 vs. K_2 O diagram. The aluminum saturation indexes(A/CNK) of the biotite monzogranites range from 1.06 to 1.19, corresponding to weakly to strongly peraluminous. They are enriched in rare earth elements(REE), high field strength elements(HFSEs; Zr,Hf). and large ion lithophile elements(LILEs; Rb, U, Th). The LREEs are enriched relative to the HREEs,with a distinct negative Eu anomaly in a chondrite-normalized REE diagram. Geochemically, the Xierzi biotite monzogranite is classified as an aluminous A-type granite, with all samples plotting within the A2-type granite field on a Y/Nb vs. Rb/Nb diagram. Zircon ε_(Hf)(t) values and two-stage modal ages of the zircons within the pluton range from +4.80 to +13.65 and from 983 to 418 Ma, respectively, indicating that the primary magma was generated through partial melting of felsic rocks from juvenile crust.Consequently, these results demonstrate that the Xierzi pluton formed under the post-orogenic extensional setting after arc-continent collision in the middle Permian.

Geochronology, Geochemistry and Sr-Nd-Hf Isotopes of Early–Middle Triassic Adakitic Plutons in Central-eastern Jilin Province, NE China: Constraints on the Non-synchronous Closure of Paleo-Asian Ocean

The Changchun–Yanji suture zone(CYSZ) in NE China is considered as the suture between the North China Craton(NCC) and Central Asian Orogenic Belt(CAOB). The geochronology, geochemistry and Sr-NdHf isotopes of Early–Middle Triassic adakitic plutions from the CYSZ, are presented in this paper to discuss their petrogenesis and tectonic setting, as well as to constrain the timing and style of the Paleo-Asian Ocean's final closure. In Early Triassic, the Dayushan pluton(ca. 250 Ma) from western CYSZ has negative ε_(Nd)(t) values, bidirectional provenances(NCC and CAOB) of ε_(Hf)(t), which are formed in a collision tectonic setting. In contrast, in eastern CYSZ, the early Triassic samples in Liangshan(ca. 242 Ma) were high Mg~# values, positive ε_(Nd)(t), single provenances(CAOB) of ε_(Hf)(t) resulting from a subduction setting. In the Middle Triassic, the Atype granites in western CYSZ are found in previous studies representing a post-collisional extensional environment, whereas syn-collisional Lianyanfeng granites(ca. 237 Ma) in eastern CYSZ with low ISr and large scale ε_(Nd)(t) and ε_(Hf)(t) values from bidirectional provenances(NCC and CAOB), represent a collisional setting. The Paleo-Asian Ocean's occurred in a scissor-like fashion along the CYSZ during the Triassic period.

Geochemistry and Tectonic History of Seamount Remnants in the Xingshuwa Subduction Accretionary Complex of the Xar Moron Area,Eastern Margin of the Central Asian Orogenic Belt

This study focuses on the geology,geochemistry,zircon U-Pb geochronology and tectonic settings of the three types of seamount basalts from the Xingshuwa subduction accretionary complex in the Xar Moron area,eastern margin of the Central Asian Orogenic Belt(CAOB).The seamount remnants are composed of carbonate’cap’sediments,large volumes of pillow and massive basalts,carbonate breccia slope facies and radiolarian cherts.Group 1 basalts are characterized by high contents of P2 O5 and TiO2 with alkaline affinity and LREE enrichment,indicating that they are derived from intraplate magma.Group 2 basalts display N-MORB LREE depletion patterns,indicating that they were formed at a mid-ocean ridge.Group 3 basalts have shown distinct Nb depletion and high Th/Yb ratios,indicating that they were generated in an island arc tectonic setting.The zircon U-Pb age of Group 1 basalt sample XWT18-131 is 576.4±9.4 Ma,suggesting that the oceanic island seamount was the product of intraplate magmatism related to a mantle plume or’hot spot’in the late Neoproterozoic.The zircon U-Pb age of Group 2 basalt sample XWT18-132 is 483±22 Ma,indicating that the Paleo-Asian Ocean(PAO)was continuously expanding in the Early Ordovician.The zircon U-Pb age of Group 3 basalt sample XWT18-101 is 240.5±8.2 Ma,suggesting that this area underwent the evolutionary path of ocean-continent transition,developing towards continentalization during the Middle Triassic.Thus,we believe that there was both mantle plume-related intraplate magmatism and intraoceanic subduction during the evolution of the PAO,the CAOB possibly being an evolutionary model of an intraoceanic subduction and mantle plume magmatism complex.

Permian tectonic evolution and continental accretion in the eastern Central Asian Orogenic Belt:A perspective from the intrusive rocks

The tectonic evolution and history of continental accretion of the eastern Central Asian Orogenic Belt(CAOB)are not yet fully understood.In this study,we investigate Permian intrusive rocks from the Jiamusi Block of the eastern CAOB to constrain the tectonic evolution and continental accretion of this region during the late-stage evolution of the Paleo-Asian Ocean.Our new data show that Early Permian gabbro-diorites were derived from the partial melting of depleted mantle metasomatized by oceanic-slab-released fluids.Middle Permian adakitic granites have low Na2O and MgO and high K2O contents,indicating a thickened-lower-crust source.Late Permian S-type granites were derived from the partial melting of continental crust.A compilation of the available geochronological data for Permian intrusive rocks(including adakitic and A-,S-,and I-type granites and mafic rocks)from the eastern CAOB reveals that the A-type granites formed mainly during the Early–Middle Permian,S-type and adakitic granites mostly during the Middle–Late Permian,and I-type granites and mantle-derived mafic rocks throughout the Permian.The A-type granites,which are proposed to have been sourced from thinned continental crust,indicate an extensional setting in the eastern CAOB during the Early Permian.The Middle–Late Permian adakitic granites imply a thickened continental crust,which indicates a compressional setting.Therefore,the eastern CAOB underwent a transition from extension to compression during the Middle Permian,which was probably triggered by the late-stage subduction of Paleo-Asian oceanic crust.Considering the petrogenesis of the intrusive rocks and inferred regional tectonic evolution of the eastern CAOB,we propose that vertical underplating of mantle-and oceanic-slabderived magmas contributed the materials for continental crust accretion.

Salt Tectonics and Basin Evolution in the Gabon Coastal Basin,West Africa

The Gabon Coastal Basin is a typical saliferous basin located in the middle portion of the West African passive continental margin. Complex salt tectonics make sedimentary sequences and structural frameworks difficult to interpret and can lead to difficulties in construction of balanced cross-sections and reconstruction of basin evolutionary processes. Sedimentary facies and salt structur- al patterns displaying zonation are based on seismic reflection profiles and drilling data. Two near-vertical fault systems, NW-SE and NE-SW, caused basin to be subdivided E-W zoning and N-S partitioning. Scarp slopes and extension faults formed in the Hinge belt III zone where salt diapir piercement occurred and numbers of salt pillars, salt stocks and salt rollers developed under transten- sion of coupled near-orthogonal fault systems. The zone east of Hinge belt III is characterized by small-scale salt domes and salt pillows. To the west are large-scale salt walls and salt bulge anticlines caused by diapirism promoted by tension and torsion that also resulted in formation of numerous salt pillars, salt stocks and salt rollers. Our modeling of salt tectonic structures indicates that they were produced by plastic rheological deformation of salt under regional stress fields that varied during three distinct phases of extension, compression and re-activation. Hinge belt III was active from Coniacian to Early Eocene, which was a critical period of formation of salt structures when many extension-related salt structures formed and salt diapirism controlled the distribution of turbidite fans. Rootless extrusion-related salt stocks developed throughout the Late Eocene to Early Oligocene as a result of lo- cal ephemeral low-intensity tectonic inversion. Post Oligocene salt diapirism was weak and salt tecton- ics had a weak influence on sedimentation. Balanced cross-sections of two saliferous horizons crossing different tectonic units from east to west reveal that the basin tectonic evolution and sediment filling processes can be divided into three stages containing seven episodes of rifting, transition and drifting.

东北地区大地构造演化与成矿制约

东北地区处于华北板块、西伯利亚板块与西太平洋板块交汇部位,是研究华北克拉通、古亚洲洋构造域、古太平洋构造域复合造山与成矿作用的重要地区.东北地区成矿地质条件优越,是我国战略性矿产资源找矿的重点片区之一.2011年以来,为保障我国资源能源可持续发展和重大基础地质问题的解决,国家逐渐加强了东北地区基础地质调查和研究工作,在东北地区主要成矿带、盆-山结合带及资源基地开展了大量1∶5万区域地质矿产调查、成矿地质背景及综合研究等工作,取得了一大批基础性和原创性地质成果,填补了东北地区中大比例尺地质调查空白.本文以“东北地区区域地质志”项目为依托,对2011年以来开展的基础地质调查项目取得的新数据和成果进行了系统梳理,总结了东北地区取得的主要基础地质研究成果或进展.在此基础上,进一步分解了华北克拉通、兴-蒙造山带等大地构造单元,恢复了古亚洲洋、鄂霍次克洋、古太平洋构造演化历史,完善了东北地区大地构造格架,并探讨了其对区域成矿作用的制约,为新一轮找矿突破战略实施提供基础地质支持.

环印度洋地区被动陆缘盆地构造沉积演化及其对成藏要素的控制作用

环印度洋周缘被动陆缘盆地油气资源潜力巨大,是当前世界油气勘探的热点地区之一。本文基于IHS商业数据库和前人研究成果等资料,厘定了环印度洋地区被动陆缘盆地构造演化史,分析了构造演化对盆地充填结构和成藏要素的影响,并利用蒙特卡洛模拟法评估了盆地油气资源潜力,优选了有利勘探区带。研究结果表明,环印度洋地区被动陆缘盆地经历了3期构造演化阶段,依次为裂前期、同裂谷期和被动陆缘期。根据盆地演化的主导阶段,研究区内被动陆缘盆地可分为拉张边缘裂前发育型、拉张边缘断坳叠置型、拉张边缘坳陷发育型和转换边缘断坳叠置型。盆地内烃源岩主要发育于裂前期—被动陆缘早期,不同地区的主力烃源岩层系不同;储集岩主要发育于裂前期—被动陆缘晚期;区域盖层则主要发育于被动陆缘期。资源评价结果显示,研究区内重点被动陆缘盆地待发现石油、天然气和凝析油可采资源量(均值)分别为4.49×10^(8) t,15.86×10^(12) m^(3)和5.23×10^(8) t,折合成油当量137.69×10^(8) t。澳大利亚西北陆架北卡那封盆地裂前中—上三叠统区带、东非地区鲁伍马盆地北部和坦桑尼亚盆地南部中白垩统—新近系三角洲-深水扇区带是最有潜力的勘探区带。

东印度洋东经90°海岭的地球物理特征和成因探讨

东经90°海岭发育于东印度洋,自孟加拉沉积扇向南穿越赤道直至印度洋南部布罗肯脊,是世界上最长的线性构造。海岭的形成机制与东印度洋晚白垩世至新生代的多阶段演化有关,由于其跨越赤道、长度大于5 000 km,南北不同区域的构造背景较为复杂,因此,其不同分段的地球物理特征也各具特色。通过分析海岭不同分段的形貌、浅层结构、重磁、地壳厚度及洋底年龄等地质地球物理数据,结合东印度洋海底扩张演化史,探讨了海岭的不同分段的成因机制。结果表明,90°E海岭的形成与板内热点活动、地幔柱-洋中脊相互作用、板块扩张与扩张中心跃迁,以及转换断层等诸多因素有关,是多种地质作用和地质过程综合作用的结果。2°N以北的海岭可能形成于远离扩张中心的印度板块内部,与板内火山作用有关联;18°S以南的部分形成于印度板块与南极洲板块边界转换断层附近;而2°N~18°S之间的中部区域则最为复杂,推测中段的形成受到了凯尔盖朗热点与沃顿扩张脊的相互作用,以及海岭下方的多次洋脊跳跃等因素的影响。分析认为,海岭中段是深入认识海岭成因机制、解决海岭构造演化和动力学机制以及脊-柱相互作用等重大科学问题的关键区域。未来在海岭中段开展地球物理测量及钻探工作,丰富海岭中段的地球物理综合数据,揭示中段不同位置岩石的物质组成与形成年代,是解决上述重大科学问题的必由之路。

西藏班戈地区侵入岩年代学和地球化学:对班公湖-怒江洋盆演化时限的制约

详细的野外地质调查、室内锆石U-Pb年代学和岩石地球化学研究显示,班戈地区侵入岩可以分为4期：早白垩世早期石英闪长岩和英云闪长岩（138Ma±）,早白垩世中期花岗闪长岩（132-128Ma）,早白垩世中晚期二云二长花岗岩（130-114Ma）,晚白垩世二长花岗岩（80Ma±）,从北到南各期次侵入岩具有成岩年龄逐渐变新,形成环境由岛弧环境→同碰撞造山环境→后碰撞环境演变。这一成果为确定班公湖-怒江洋盆的俯冲极性及演化时限提供了新的资料。班戈地区班公湖-怒江洋盆在中侏罗世之前已开始向南俯冲消减,这种俯冲消减活动一直持续至早白垩世中期最终闭合（130-125Ma）,拉萨地体与羌塘地体开始发生碰撞作用,这种碰撞作用大约持续了20-30Myr,在晚白垩世早期进入后碰撞阶段（100-80Ma）。

新疆南天山构造格架及构造演化

南天山碰撞造山带位于西伯利亚与塔里木地块之间的北亚造山区南部的天山造山系的中南部,是塔里木地块与哈萨克斯坦-准噶尔地块之间的一条构造带,地理上由哈尔克山、额尔宾山、虎拉山等组成,地质上主要由古生代地质体组成,其南北两侧均为活动陆缘,中间由洋壳残片、洋岛和增生杂岩组成,是南天山古生代洋盆演化的产物。南天山古洋盆从震旦纪裂解,寒武纪持续扩张,奥陶纪—石炭纪向南北两侧俯冲闭合,至二叠纪南天山造山带进入后造山调整阶段。

东昆仑南缘布青山构造混杂岩带的地质特征及大地构造意义

在1∶50000地质填图的基础上,运用详细的野外剖面测制、岩石组合分析、LA-ICP-MS锆石U-Pb同位素定年等研究手段,将东昆仑南缘布青山构造混杂岩划分为基质和构造混杂岩块。构造混杂岩块包括变质基底岩块、洋壳型岩块和岛弧型岩块。其中,洋壳型混杂岩块又细分为早古生代蛇绿岩(516.4Ma±6.3Ma)、晚古生代蛇绿岩(332.8Ma±3.1Ma)和海山/洋岛玄武岩;岛弧型混杂岩块细分为加里东期中酸性侵入岩岩块(441.1Ma±6.3Ma)和火山熔岩岩块。建立了东昆仑南缘布青山构造混杂岩带2套典型的古洋盆扩张、俯冲消减的物质组合,分别代表东原特提斯洋和东古特提斯洋的形成与演化,从而为研究东特提斯洋演化的进程提供了新证据。

新疆北部古生代构造演化的几点认识

最近的地质调查和研究资料揭示,新疆北部古生代存在"三块两带"的构造格局,并经历了复杂的洋陆转换过程。地质、地球物理和碎屑锆石年龄结果显示,准噶尔盆地南部应存在一个至少发育前震旦系的古老陆块;初步认为东准噶尔北自额尔齐斯构造带东南的玛依鄂博地区至南部的卡拉麦里构造带南界,整体为一增生杂岩体,西准噶尔自额尔齐斯构造带南缘至谢米斯台南缘亦为一增生杂岩体。提出新疆北部加里东运动表现为准噶尔-吐哈陆块、中天山陆块群、伊犁地块等拼合形成哈萨克斯坦板块的一部分。从新疆北部泥盆系建造组合和沉积环境演变视角,探讨了早古生代形成的哈萨克板块北部洋盆从早泥盆世开始,至晚泥盆世拼合,洋盆经历了逐渐变浅直至消亡的演化过程。结合区域地质调查资料,提出南天山为一巨大的增生杂岩体,代表了哈萨克斯坦板块与塔里木板块最后增生拼合的位置,亦是古亚洲洋在中国境内最后闭合的位置,闭合的时限为早石炭末期。在以上认识的基础上,提出新疆北部晚古生代构造演化的"三块两带"基本框架:即在统一哈萨克斯坦板块形成后,自北而南依次存在西伯利亚板块、哈萨克斯坦板块、塔里木板块及其间的准噶尔洋盆和南天山洋盆。晚泥盆世哈萨克斯坦板块与西伯利亚板块完成增生拼贴;早石炭世末,塔里木板块与西伯利亚-哈萨克斯坦联合板块完成增生拼贴,古亚洲洋结束洋陆转换;晚石炭世至早二叠世,新疆北部进入后碰撞伸展至大陆裂谷演化阶段。

新疆西天山博罗科努成矿带岩浆岩时空分布、构造演化与成矿响应

博罗科努成矿带位于新疆西天山北缘,近年来找矿成果突出。在充分收集前人研究成果的基础上,初步总结了博罗科努带岩浆岩时空分布特点及其年龄资料,重点分析了与成矿关系密切的晚古生代岩浆作用的性质。博罗科努带地质历史与北天山洋的演化密切相关,前寒武纪统一基底形成,北天山洋打开。寒武纪为被动陆缘环境,北天山持续扩张。奥陶纪北天山洋向伊犁地块之下俯冲,该带进入大陆弧演化阶段。泥盆纪—晚石炭世早期为俯冲高峰期,引发了一系列钙碱性的岩浆活动;早二叠世该带已进入陆相环境,但北天山洋残余洋盆的俯冲持续到中二叠世;晚二叠世全面进入陆内演化阶段,区域构造应力性质由挤压变为伸展。伴随洋-陆构造演化,形成了莱历斯高尔和阿希两大矿集区,分别对应2套成矿系统:与侵入岩浆活动有关的矽卡岩-斑岩-热液脉型铁、铜、钼、金、锑、铅、锌成矿系统和与次火山热液活动有关的浅成低温热液-斑岩型金、铅、锌、铜成矿系统。