Provenance and tectonic setting of the Gudongjing Group in Beishan OrogenSCIEI北大核心CSCD

增生造山带中陆源碎屑岩物源区特征的研究可为解剖造山带结构甚至大陆地壳的形成和演化提供关键证据。北山造山带中部的古硐井群被认为是前寒武纪稳定沉积盖层,是北山造山带存在微陆块的重要依据。本文围绕古硐井群的物源区特征,进行了碎屑颗粒和重矿物统计、全岩主微量元素地球化学分析、碎屑锆石U-Pb年代学和Hf同位素测试。古硐井群碎屑岩的碎屑颗粒多呈棱角状,主要为石英、长石,同时含大量硅质岩碎屑和一定数量的火山岩碎屑;重矿物组成以褐铁矿、锆石、白钛石、尖晶石为主,角闪石、电气石、辉石次之,暗示物源区可能存在蛇绿岩、增生杂岩。全岩主量元素以高硅、高铝、富碱、低锰为特征,结合REE、Cr、Co、Sc和Th等惰性元素含量特征共同指示了长英质的物源区。最年轻的碎屑锆石年龄为443.9±13Ma,表明古硐井群最大沉积时限为晚奥陶世。碎屑锆石的年龄高度集中于470Ma附近,且该区间锆石ε_Hf(t)值多为正值,指示物源区存在大量新生地壳物质。本文推测古硐井群可能形成于增生楔楔顶盆地;研究结果支持北山造山带是古生代持续增生造山的产物这一认识。     

Pre-Cenozoic tectonic attribute and setting of the Song Da zone,VietnamEI北大核心CSCD

Rock association and regional unconformity are identified based on field survey and mapping for the stratigraphy, tectonics, metamorphic rock and igneous rocks in the Song Da zone, the northwestern Vietnam. Pre-Cenozoic in the Song Da zone is divided into three structural layers: (1) the Presinian crystalline basement, (2) the Cambrian-lower part of Upper Triassic, and (3) the upper part of Upper Triassic-Cretaceous. The Pre-Cenozoic structural successions of the Song Da zone show similar features with those of the Yangtze-South China plate: (1) In the Presinian, both of them have TTG complex and Khondalite series of similar ages and experienced similar tectonic evolution; (2) In the Cambrian-early Upper Triassic, the phosphorite and thick-layered limestone are comparable, and the Permian-Triassic basalt in the Song Da zone has genetic mechanism similar to that of the Emeishan basalt; (3) In the late Upper Triassic-Cretaceous, the volcanic-sedimentary faulted basins and thick continental red beds are comparable to those in East China. It can be concluded that the Song Da zone should have been part of the southwestern Yangtze-South China plate, and the boundary between the Yangtze-South China plate and Indochina plate is the Song Ma suture zone which contains ophiolite remnants. Tectonic settings of different structural layers indicate that the Song Da Zone experienced geological events such as the Columbia and Rodinia Supercontinent, sedimentation of the stable platform cover, closure of the Paleo-Tethys, and NW subduction of the Paleo-Pacific plate to the Eurasian plate. The Pre-Cenozoic basement of the Yinggehai Basin is the seaward extension of the Song Da zone, which shows similar tectonic features.     

Late Paleozoic tectonic -magmatic evolution history of the northeastern ChinaSCIEI北大核心CSCD

Northeastern China is suited in the eastern part of the Central Asian Orogenic Belt, and it is mainly composed of Erguna Massif, Xing'an Massif, Songnen-Zhangguangcai Range Massif, Jiamusi Massif, and Nadanhada Terrane. The Late Paleozoic magmatism was relatively intense accompanied with multiple stages of amalgamation in several microcontinents, therefore these magmatic products are an important media in recording the Late Paleozoic tectonic evolution history of the northeastern China. According to the petrological, geochronological, and geochemical characteristics of Late Paleozoic igneous rocks in the northeastern China, we found that the Late Paleozoic magmatism was based on Carboniferous -Permian igneous rocks. The Early Carboniferous magmatic products are gabbro, diorite and granite, the Late Carboniferous magmatic products are mainly composed of granitoids with minor gabbro, and the Permian magmatic products are mainly granitoids. Meanwhile, these Late Paleozoic igneous rocks mostly exhibit typical arc characteristics. In addition, the Late Paleozoic igneous rocks in eastern Jilin and Heilongjiang provinces are mainly Permian granitoids with minor gabbro, and these Permian igneous rocks show typical arc characteristics. Combined with petrological, geochronological, geochemical and isotopic characteristics, we suggest that the Late Paleozoic igneous rocks in the Great Xing'an Range and eastern Jilin and Heilongjiang provinces underwent different magmatic evolution history, and the microcontinents in NE China had different crustal growth history.     

Geochemistry and tectonic environment of amphiholites of the Zanhuang metamorphic complex北大核心

Amphibolites, one of the kinds of Precambrian basement rocks, are exposed in the south-middle Zanhuang Metamorphic Complex, central-south segment of the Trans-North China Orogen. These metamorphic rocks were carefully studied through field investigations and petrographical and geochemical analyses. It was found that protoliths of the Zanhuang amphibolites are calc-alkaline and tholeiitic rocks with a large range of ΣREE (41.38 × 10-6 -232.55 × 10-5 ) and weak LREE enrichment. The multi-element variation results showed that K, Rb and Ba were relatively concentrated, Nb and Ta were of evident depletion while Ti was of weak depletion. Geochemical characteristics and various relevant geochemical discrimination diagrams showed that the Zanhuang amphibolites were formed in volcanic arcs of continental margin similar to the current continental margin, which was resulted from the subduction between the Western Block and the Eastern Block.     

Paleozoic sedimentary processes and magmatism in Zamenwude area,Mongolia, and their implications for tectonic evolution of the Xingmeng orogenic beltSCIEI北大核心CSCD

兴蒙造山带属于中亚造山带的东段,关于其演化过程存在两种主要观点:一种观点认为它是由古亚洲洋经历整个古生代的连续俯冲-碰撞过程后在早三叠世形成;另一种观点则认为古亚洲洋在晚泥盆世之前就通过俯冲-碰撞过程闭合,形成早-中古生代造山带,随后在石炭-二叠纪又经历了从陆内伸展到再次闭合的过程,并形成陆内造山带。蒙古国东南部扎门乌德地区出露各类古生代沉积岩和岩浆岩,可以为解决上述争议提供典型研究实例。本文通过沉积学、年代学和地球化学等多种手段综合研究,取得以下研究成果:(1)根据年代学和岩性特征,在该地区识别出三类古生代岩石组合,第一类是以黑云母二长花岗岩为代表的中志留世侵入岩,第二类是中泥盆世大套的粗碎屑岩-火山岩沉积旋回,第三类是不整合地沉积于早期造山带之上的二叠纪巨厚火山-沉积岩系。这三类岩石组合分别属于俯冲阶段的大陆边缘岛弧带岩浆岩、碰撞造山后期的上叠盆地以及叠加在早期造山带岩石圈之上的晚古生代陆内伸展时期的裂谷盆地的沉积。(2)利用研究区所有古生代碎屑锆石和岩浆岩全岩资料,揭示了该地区古生代时期地壳厚度变化趋势如下:500~425Ma的俯冲-碰撞过程造成地壳加厚;425~375Ma的碰撞造山后伸展过程使地壳变薄;375~350Ma地壳再次加厚,可能与造山带物质堆叠有关;350~275Ma地壳再次减薄,对应于广泛而强烈的晚石炭世-早二叠世火山岩,证明此时期岩浆活动的构造背景是区域伸展而不是挤压作用。(3)根据研究区出现的三类岩石组合特点,结合研究区以南的艾力格庙地区已有的研究成果,可以划分出五个早-中古生代造山带构造单元和两个叠加其上的晚古生代陆内造山带构造单元,揭示蒙古国扎门乌德地区经历了早-中古生代加积造山带和晚古生代陆内造山带等两个构造演化过程。本文研究为认识兴蒙造山带的两阶段构造发展提供了新资料。     

Zircon U-Pb gcochronology and geochemical characteristics of the reshui monzogranite in the eastern kunlun and their tectonic significances北大核心CSCD

In order to probe the genesis and tectonic significance of the granite in the Reshui area, geoehronologicai and geochemical studies of the Reshui monzogranite have been carried out in this paper. The results show that the Reshui monzogranite has LA-1CP-MS zircon U-Pb age of 231 ±1 Ma, indicating that it was formed in late Triassic. It has high contents of Si()2(68. 74%-7l.69%) , Al,(),( 14. 78%-15. 18%). and k,()( 3. 78%-4. 32% ) , with k,()/Na,() ratios ranging from 1. 05 to 1. 32 ,r Rttmann indexes ranging from 1. 87 to 2. 21 . and A/CNk values varying from 1. 03 to 1. 07, respectively. Thus, the Reshui monzogranite belongs to the high k calc-Alkaline weak peraluminous granite. In addition, it has total REE contents(ΣREE) of I 18. 28x 10-6 - 148. 1 x 10-6, with right declined REE distribution patterns showing strong enrichment of LREE and relative depletion of HREE. Its large ion lithophile elements( L1LE) , including Rb. Ra, Th, and l.REE are enriched, while its high field strength elements( HESE) , including Nh, Ta, P. and Ti, are relatively depleted. It has characteristics of the 1-Type granite. It could be mainly sourced from the partial melting of the subducted slab or basic rocks of the lower crust, mixed partly with mantle materials. Combining with regional geological background, it is believed that the Reshui monzogranite was formed by the interaction of the crust and mantle under the tectonic environment of collision-post collision.     

Migration-circulation processes and enrichment-mineralization mechanism of lithium-beryllium elements in the continental crust.SCIEI北大核心CSCD

锂铍金属是世界关键金属资源,矿床类型多样,成矿作用发生在大陆地壳。但大陆地壳中锂铍元素的迁移-循环规律及不同锂铍矿床间的成因联系尚不清楚。本文系统地总结与梳理了大陆地壳结构与物质循环特征和不同类型锂铍金属矿床间的成因联系,提出大陆地壳锂铍循环-成矿系统的概念与模型,并将大陆地壳锂铍的迁移与循环划分为四个过程:变质过程、深熔过程、花岗岩浆过程、花岗质岩浆岩风化、淋滤与蚀变的浅-表生过程。沉积岩中锂铍元素在变质过程中可富集到一些变质矿物中,一些富锂铍黏土矿物也在变质过程转变成新的富锂铍变质矿物(如绿泥石、云母与堇青石);地壳深熔过程使得锂铍元素从变质矿物中释放出来并聚集在花岗岩浆中,麻粒岩相深熔(如黑云母脱水熔融与堇青石分解熔融)可能是锂铍大规模成矿的主要熔融方式;绝大多数锂铍矿床与花岗岩浆及其岩浆岩有关,是花岗岩浆与花岗质岩浆岩在不同演化阶段与不同方式富集成矿的结果;浅-表生过程对锂铍花岗岩-伟晶岩和流纹岩与流纹质凝灰岩的物理化学改造,可形成盐湖卤水型锂矿床、黏土型锂矿床以及各种次生锂铍矿床。变质过程中锂铍的迁移与富集机制,大型-超大型花岗岩-伟晶岩型锂铍矿床形成条件与关键控制因素等问题,是亟待研究与思考的科学问题。     

The Permian mafic intrusive events in the northwestern margin of the Tarim Basin and their tectonic significanceSCIEI北大核心CSCD

塔里木大火成岩省是我国境内发现的两个重要的二叠纪大火成省之一,不仅有大规模的溢流相玄武岩喷发,还有复杂多样的侵入岩及其组合。以往的研究主要集中在二叠系等显生宙地层发育区,对于前寒武系等古老层系中是否存在二叠纪岩浆侵入未引起重视。本文通过野外地质调查,在阿克苏地区前寒武系中识别出数条侵入南华系的基性岩墙和较大规模侵入震旦系的基性岩床。岩墙、岩床与围岩之间均显示出典型的侵入接触关系,包括岩体内部结晶粗、边部结晶细的淬冷边结构、岩床顶底面显著的切层现象以及包裹围岩团块等;显微镜下观察表明,辉绿岩具有典型的辉绿结构和嵌晶含长结构。锆石U-Pb年代学结果表明,侵入下震旦统的辉绿岩岩床和侵入南华系的辉绿岩岩墙的侵位时代在误差范围内基本一致,约为290Ma。岩石地球化学特征表明,辉绿岩岩床具有与洋岛玄武岩(OIB)相似的稀土及微量元素配分模式,结合Sr-Nb-Pb同位素测试结果,认为它们来源于碳酸盐化的富集型岩石圈地幔部分熔融,而辉绿岩岩墙具有Nb、Ta、Zr、Hf等负异常的地球化学特征,可能来自曾被俯冲相关流体/熔体交代的岩石圈地幔源区。本文的早二叠世辉绿岩岩床和岩墙的形成时代、岩浆源区和岩浆演化...     

Decoupling of cobalt and nickel in high-temperature magmatic processes and its metallogenic indicationSCIEI北大核心CSCD

Cobalt ( Co) and nickel (Ni) have similar geochemical behaviors and commonly co -vary in nature, but they may undergo decoupling in certain geological processes, especially in ore -forming processes, and the decoupling mechanism is not yet clear. This paper analyzes the distribution characteristics and migration behaviors of Co and Ni in major rock -forming minerals in different types of mafic-ultramafic rocks. The Ni (2500 x 10(-6) 3400 x 10(-6)) and Co (110 x 10(-6) 160 x 10(-6)) contents of mantle olivine are both higher than those of the primitive mantle. The Ni content shows no obvious correlation with the Fo value, while the Co content has a strong negative correlation with both the Fo value and the Ni/Co ratio. This indicates that partial melting does not cause significant changes in Ni content of olivine, but can control the Co content and the Ni/Co ratio, mainly due to the differences in compatibility between the two elements in olivine. Melt-rock reactions can cause significant Co-Ni decoupling between minerals and within minerals, but the mechanisms differ. In the process of reacting with basaltic magma, olivine mainly absorbs Co and loses Ni, while being affected by coexisting spinet minerals. When reacting with carbonatite melt, olivine loses Co, but Ni remains almost unchanged. As mantle derived basaltic magma intrudes into the lower crust, the migration of Co and Ni in pyroxenes is controlled by concentration gradients and sulfide crystallization. The local enrichment of Co provides an important material basis for the formation of Co -rich melts in deep crustal melting. During the differentiation and evolution of mafic-ultramafic magma, the chromite fractional crystallization and sulfide segregation can cause Co-Ni decoupling at both rock and/or mineral scales. Meanwhile, the enriched hydrous fluids released during chromite aggregation and sulfide melt solidification can significantly promote the efficiency of element exchange in sub-solidus state, especially strengthening the activity of Co, thus causing negative correlations between Co and Ni in olivine and even in chromite. Comparative studies show that the trends of Co and Ni content changes in mineral assemblages are evidently different, or even opposite, between mineralized and barren bodies and between ore -bearing and ore -free rocks, which provides a basis for identifying mineralization in rock bodies and guiding prospecting.     

Petrology,geochemistry and metamorphic evolution of Lancang Group in the Changning-Menglian complex belt and its implications on the tectonic evolution of the Paleo-TethysEI北大核心CSCD

Lancang Group within the Changning-Menglian complex belt in the Sanjiang area, Yunnan Province involves many kinds of meta-sediments, including staurolite-kyanite-bearing garnet-mica schist, garnet-mica schist, chloritoid-white mica schist and chlorite-glaucophane-albite schist. Detailed petrographic observation, mineral chemistry analysis and phase equilibrium modelling have shown that these meta-sediments preserve distinctly metamorphic evolutions. The staurolite-kyanite-bearing garnet-mica schist records the decompression and cooling histories related to retrograded metamorphic processes from middle-temperature eclogite facies to amphibolite facies with a peak mineral assemblage of garnet + kyanite + phengite + jadeite formed at the P-T condition of about 19 similar to 30kbar and 600 similar to 750 degrees C. For the garnet-mica schist, the peak metamorphic mineral association constrained by X-Prp and X-Grs in garnet, and Si content in phengite includes garnet + phengite + omphacite + lawsonite + paragonite and the related P-T condition is around 17 similar to 19. 5kbar and 430 similar to 475 degrees C . The chloritoid-white mica schist is characterized by the mineral assemblage of chloritoid + phengite + paragonite + chlorite whereas the peak mineral assemblage includes phengite + paragonite + carpholite. The peak P-T condition defined by Si content in phengite is limited in the range of 17 similar to 19kbar and 300 similar to 330 degrees C. Both garnet-mica schist and chloritoid-white mica schist consistently record heating and decompression processes from lawsonite-blueschist facies to epidote-blueschist facies. Metamorphic reactions and mineralogy of chlorite-glaucophane-albite schist roughly give the P-T condition of 9 similar to 11kbar and 430 similar to 520 degrees C. Studies on the geochemistry of Lancang Group reveal that these meta-sediments show the geochemistry affinity to the continental arc, active continental margin and upper crust sediments. The protoliths are mainly mud rock and sandstone with low maturity and a little of mafic-intermediate volcanic rock. The sediment sources are predominantly intermediate-acid magmatic rocks with old sedimentary contamination to different degree. Tectonic discrimination diagrams show that meta-sediments in the Lancang Group are mainly derived from the continental island arc or active continental margin tectonic setting. Combined with the metamorphism and geochemistry characteristics of these rocks in the Changning-Menglian complex belt, it is therefore inferred that the meta-sediments of Lancang Group display various metamorphic evolutions. Lancang Group are considered to have experienced multi-phase/stage and complex tectonic evolution histories.     

The feature and tectonic setting of Dongqiao podiform chromitite in the central segment of the Bangong Lake-Nujiang suture zone in TibetSCIEI北大核心CSCD

早侏罗世东巧蛇绿岩位于班公湖-怒江缝合带(班怒带)东段,蕴含较为丰富的豆荚状铬铁矿资源。东巧地幔橄榄岩主体由方辉橄榄岩组成,铬铁矿赋存在其内部的纯橄岩脉中。方辉橄榄岩和纯橄岩均显示出弧前橄榄岩的特征。方辉橄榄岩中橄榄石的Fo值为89.8~92.2,斜方辉石的和单斜辉石的Mg^(#)值分别变化于89.7~92.0和92.7~95.1,铬尖晶石的Cr^(#)值(Cr^(#)=100×Cr/(Cr+Al))为60.8~75.9;纯橄岩中橄榄石的Fo值为91.7~92.5,斜方辉石Mg^(#)值变化于91.7~92.1,单斜辉石的Mg^(#)值变化于94.0~94.6,铬尖晶石的Cr^(#)值为69.0~83.1。铬铁矿主要呈致密块状和浸染状构造,其中铬尖晶石的矿物包裹体有橄榄石、斜方辉石、单斜辉石、角闪石和铂族矿物等。矿石中的铬尖晶石与橄榄岩中的铬尖晶石相比,具有较高的Cr^(#)值(72.5~86.9)和Mg^(#)值(52.8~70.5),较低的Al_(2)O_(3)(6.25%~13.6%)、TiO_(2)(0.06%~0.16%)和Zn(518×10^(-6)~714×10^(-6)),属于高铬型铬铁矿,平衡熔体与玻安质熔体有亲缘性。方辉橄榄岩中铂族元素(PGE)总含量(14.01×10^(-9)~32.81×10^(-9))近似于原始地幔,IPGE(Os、Ir和Ru)/PPGE(Rh、Pt和Pd)的比值均大于1;纯橄岩的PGE总量(13.36×10^(-9)~16.08×10^(-9))略低于原始地幔,IPGE和PPGE富集程度近似;铬铁矿的铂族元素总量(108.4×10^(-9)~645.7×10^(-9))远远高于原始地幔和地幔橄榄岩中PGE的含量,且IPGE以及Rh相对原始地幔富集,而Pt和Pd相对亏损,具明显右倾特征的配分模式,指示东巧地幔橄榄岩和铬铁矿形成过程经历了熔体抽取和交代作用。通过与全球典型豆荚状铬铁矿矿床的特征对比,认为班怒带的蛇绿岩应该有良好的铬铁矿成矿背景。     

Analysis of tectonic stress field and potential activities in Lingshan Fault Zone,GuangxiEI北大核心CSCD

Tectonic stress is one of the most active factors in the earth crust, therefore figuring out its mode of action and form of conversion is of great significance to guide the research on fault activity. Through a survey on many structural features in the Lingshan area, which include vertical folds, conjugated joints and scratch on faults surface, etc., we investigated the revolution characteristics of the tectonic stress field, mode of action and sequence of tectonic stress in the Lingshan area by structural analysis method. The results show that the region experienced four periods of function of tectonic stress field which came from four different directions: NW, NE, nearly EW and nearly SN. The force of NW appeared early than that of NE, and then the compression of nearly EW. We concluded that the structural framework of the study area has been formed by the effect of SN compressed stress which is still active today. Meanwhile, based on the geologic analysis of the mechanism of tectonic stress, we analyzed the structural stress quantitatively in the Lingshan area using finite element numerical simulation. The simulation demonstrated that the overlapping parts of strain intensive zone in higher value of maximum principal stress and lower value of maximum principal stress, such as, fault-bend parts, the fault intersections and the faults disappears site, have higher energy and prone to reactive in the later period. We think that the north of Mountain Luoyang, Fengtong, Tieling, Luwu are high stress concentration area, and the energy release is minor. And thus, we proposed a high-risk district and a sub-high-risk district in the Lingshan area is according to the size and scope of the stress. ©, 2015, Science Press. All right reserved.     

Structure of the Earth’s crust and tectonic evolution history of the Southern Indian Ocean (Antarctica)

The Southern Indian Ocean comprises large sedimentary basins of the Riiser-Larsen Sea (western sector); the Cosmonauts, Cooperation (Commonwealth), Davis seas (central sector); and the Mawson-d’Urville seas (eastern sector). The main tectonic provinces of the Southern Indian Ocean (Antarctica) have been outlined as a result of comprehensive interpretation of the geophysical data. Special attention is paid to determining the boundary between the rifted continental and oceanic crust. The basin of the Riiser-Larsen Sea was formed in the Early Jurassic under the action of the Karoo mantle plume. The intrusive complex, as a remote manifestation of the mantle plume, occurs along the inner boundary of the marginal rift. Opening of the ocean in the basin of Riiser-Larsen Sea started about 160 Ma ago and was characterized by rearrangement of plate motion and intense volcanic activity at the early stage. In the basin of the Cosmonauts, Cooperation, and Davis seas, the final stage of rifting was accompanied by the rise of the lithospheric mantle and by intrusive magmatism. The opening of the ocean started here 134 Ma ago. Emplacement of the Kerguelen plume resulted in jumping of ridges and detachment of continental crustal blocks from the Indian margin with the formation of the Kerguelen Plateau (microcontinent). The basin of the Mawson-d’Urville seas has evolved under conditions of long-term rifting since the Late Jurassic and is characterized by an extended zone of mantle unroofing. Breakup of the lithosphere between Australia and Antarctica developed asynchronously over a time interval of 95–65 Ma ago with propagation of MOR from the west eastward. The research was carried out using a great body of geophysical information (～140000 km of CDP seismic profiling, more than 250 stations of seismic refraction sounding, and more than 250000 km of magnetic and gravity profiles) obtained by expeditions from many countries over more than 30 years.     

Lower Paleozoic detrital zircon U-Pb geochronological characteristics of the Baoshan Block in western Yunnan and its constraints on the Proto-Tethys tectonic evolutionSCIEI北大核心CSCD

滇西保山地块是东特提斯构造域的主要微陆块之一,但对其物源和古地理位置仍存在较大争议。本文通过对保山地块西缘早古生代地层进行碎屑锆石U-Pb定年来约束其物源及古地理位置,并进一步探讨原特提斯洋早古生代构造演化模式。保山地块西缘早古生代地层具有相似的年龄分布模式,主年龄峰期为-0.95Ga、次级年龄峰期为-1.2Ga和-2.5Ga。寒武系公养河群最小锆石年龄为526Ma,结合其上部年龄为499.2Ma的火山岩夹层,约束其沉积时代为早寒武世早期。对比保山地块不同区域早古生代地层的碎屑锆石年龄数据,它们都具有相似的锆石年龄分布模式和年龄峰值。-0.95Ga主年龄峰期和-2.5Ga的次级年龄峰期指示保山地块早古生代的沉积物主要来自于印度大陆,而-1.2Ga的次级年龄峰期表明有部分沉积物来自于西澳大利亚,其早古生代古地理位置位于印度和西澳大利亚之间。结合沉积学证据及滇西地区广泛发育的早古生代岩浆作用,本文认为早古生代冈瓦纳大陆北缘为活动大陆边缘。     

Types and genetic mechanism of chrysoberyl depositsSCIEI北大核心CSCD

金绿宝石作为一种铍矿物,不仅能用于高新科技、军事、医疗等领域,也是一种珍贵的宝石。自十八世纪被发现以来,金绿宝石成因和矿床特征被广泛地关注与研究。本文梳理与归纳了金绿宝石矿物学特征、矿床类型与分布,并给出新的矿床划分方案;总结了金绿宝石矿床的形成机制和影响因素等方面研究进展及科学问题。金绿宝石矿床按照成因可分为四个大类,即熔体结晶类、变质成因类、交代成因类和风化成因类;而根据赋存岩石,可将金绿宝石矿床进一步划分为六种亚型,分别是花岗岩-伟晶岩型、变质伟晶岩型、蛇纹岩型、云母岩型、条纹岩型和砂矿型。金绿宝石可在高温的高分异花岗岩岩浆中直接结晶形成,主要与石英、长石、白云母、绿柱石等共生,也可见锌尖晶石、夕线石和红柱石;在高级变质条件下金绿宝石由绿柱石分解得到,在变质伟晶岩型中金绿宝石与长石和石英共生,而在蛇纹岩型中金绿宝石与硅铍石共生;由远端交代作用控制形成的条纹岩型金绿宝石常与萤石、硅铍石和塔菲石共生,而由近端交代作用控制形成的云母型金绿宝石则与金云母、绿柱石和硅铍石共生。金绿宝石矿床仍存在很多有待解决与深入探讨的科学问题：金绿宝石形成的温压范围比较大,可能存在不同晶体相;针对花岗岩-...     

Geochronology,Geochemistry and Petrogenesis of the Pungco Ophiolite,TibetEI北大核心CSCD

Although the middle section of the Bangong-Nujiang suture zone has been intensively investigated, its tectonic framework and evolution is still controversy. The Pungco ophiolite has a relative complete ophiolitic complex, which is an ideal specimen for studying this tricky problem. LA-ICP-MS U-Pb dating of zircons from the diabasic rock yielded an age of 159.0±2.1 Ma. This age suggests that the Pungco ophiolite was formed in the Late Jurassic, indicating the development of the Late Jurassic ophiolite in the third ophiolitic subzone. The whole-rock major and trace element compositions of diabasic and basaltic rocks exhibit mixed arc and N-MORB geochemical characteristics. Two diabasic samples have (87Sr/86Sr)i values of 0.7055 and 0.7063 and εNd(t) values of 11.28 and 11.84, respectively. The geochemical signatures and formation age of the Pungco ophiolite suggest that this ophiolite was probably produced in an active continental fore-arc setting. It originated from a N-MORB-like depleted mantle source with the involvement of subducted-slab fluids. Considering the regional geological background, the Pungco ophiolite was likely generated during the southward subduction of the Bangong-Nujiang Tethyan oceanic lithosphere beneath the Lhasa terrane, and belongs to a regional archipelagic arc-basin system together with the other Early Jurassic-Early Cretaceous ophiolites from the northern Tibet Lake district. © 2018, Science Press. All right reserved.     

Numerical Modeling of the Effect of Mantle Plume on Continental Drift: Revelation of the Rapid Drift of the Indian Tectonic Plate in Late CretaceousEI北大核心CSCD

Numerical modeling is used to investigate the interaction between mantle plume and continental lithosphere, especially the effect of the continental lithosphere structure, the scale and position of mantle plume on the rate of continental drift. Numerical results show that, under the effect of mantle plume, the existence of a thick root of the continental lithosphere affects the rate of continental drift. Moreover, under identical scale of mantle plume, the drift rate decreases with increasing thickness of the root. Besides, the velocity and distance of a continental plate drift are negatively correlated in scale of the continental lithosphere, but correlated with the scale of the mantle plume. For the model without lithospheric root, the mantle plume has a more appreciable impact on the plate drift rate when it comes closer to edge of the continental plate. Our models show that mantle plume can accelerate the continental drift by more than 10 cm/a. The modelling results can provide significant dynamical constraint and geological enlightenment. © 2018, Science Press. All right reserved.     

Temporal and spatial distribution,deposit type and tectonic setting of East Tianshan tungsten deposit. Acta Petrologica SinicaSCIEI北大核心CSCD

东天山是中亚增生造山带的重要组成部分,蕴含了重要的铁、铜、镍、铅锌、金、钼、铷等矿床。近年来,东天山地区陆续发现了十余个大中型钨矿床,有望成为重要的钨矿资源基地。本文介绍了东天山地区钨矿床的地质特征、时空分布与构造背景,总结了东天山钨矿成矿规律,开展了成矿预测。东天山地区钨矿类型主要包括矽卡岩型、石英脉型及云英岩型,钨矿床的空间分布明显受控于前寒武纪结晶基底,成矿时间主要聚焦于三叠纪和晚石炭世。其中,中天山地块的矽卡岩型钨矿和东南缘的石英脉型钨矿形成于三叠纪,而中天山西南缘的矽卡岩型钨矿形成于晚石炭世,均与洋盆闭合之后的碰撞造山作用有关。根据东天山地区钨矿成矿规律,本文认为东天山地区钨矿找矿潜力巨大,提出了“前寒武纪基底+花岗岩+化探异常”的钨矿找矿预测思路,针对不同尺度的钨矿找矿勘查提出了建议。     

Structural characteristics and active time of the Kangmar detachment,southern TibetEI北大核心CSCD

The Kangmar gneiss dome, typical of the north Himalayan gneiss domes, is composed of three tectono- lithologic units separated by an upper and a lower detachment fault (Kangmar detachment fault). The low-grade metamorphic Tethyan Himalayan sedimentary sequence formed the upper unit above the brittle upper detachment fault. The mylonitic granites and two-mica granites made up the lower unit beneath the ductile lower detachment fault. The mylonitc middle-grade garnet two-mica schist and biotite-plagioclase gneiss constituted the middle unit inbetween the two detachment faults and were involved in the ductile deformation of the Kangmar detachment fault. The meso- and micro-scale structural analyses on the tectonites from the detachment fault zone indicated that the Kangmar detachment fault experienced a top-down-to-north shear. Integrating macro-/micro-analyses of petrology and mineralogy, this study adopts 40Ar/39Ar dating method to constrain the active time of the Kangmar detachment fault. Analyses of the syn-deformation muscovite from the mylonitic garnet two-mica schist yield a 40Ar/39Ar plateau age of 13.23±0.15 Ma, representing the active time of the Kangmar detachment fault. The chronological result hints that the Kangmar detachment was synchronous with the south Tibet detachment systems to the south and was probably part of the south Tibet detachment systems exposed in the Tethyan Himalayan sedimentary sequence. However, this hypothesis needs from the supports of more geological and geophysical evidence. ©, 2015, Science Press. All right reserved.     

Geochemical characteristics and petrogenesis of the Dashipo-Heishantuo batholith in Beijing and its geological significanceEI北大核心CSCD

The early Jurassic Dashipo-Heishantuo batholith in Beijing, which consists of the Dashipo hornblende-biotite syenite and Heishantuo granite, exposed in the western Yanshan orogenic belt, eastern North China Craton. The Dashipo syenite is magnesian potassic intermediate rock enriched in large ion lithophile elements such as Rb, Ba, Sr, Pb and LREE, and relatively depleted in high field strength elements such as Nb, Ta, U, Th, Zr, Hf as well as P and Ti, with εNd(t) values from -12.1 to -12.2 and ISr values of 0.70506-0.70464. The Heishantuo granite is magnesian peraluminous high K calc-alkaline, with an enrichment of large ion lithophile elements and radioactive elements such as Rb, Ba, Th, U and Pb, and a depletion of HREE and high field strength elements such as Nb, Ta, Zr and Hf as well as Sr, P and Ti, with εNd(t) values from -15.5 to -18.0 and ISr values of 0.70516-0.70593. The magma of the Dashipo syenite is produced by fractional crystallization of mantle-derived K-rich mafic magma under high pressure. The partial melting of the lower crust, which was heated and metasomatised by the mantle-derived magma, produced granitic magma that intruded into the unconsolidated Dashipo syenite to form the concentric batholith. The petrology and geochemistry of the Dashipo hornblende-biotite syenite indicate that the water weakening was important for the lithospheric destruction within the interior part of the North China Craton. Meanwhile, the partial melting related to the double-diffusion of energy and chemical composition between mantle-derived magma and crustal rocks was an important mechanism for the Mesozoic calc-alkaline felsic magmatism occurred in the interior of the North China Craton. ©, 2015, Science Press. All right reserved.