云南富宁安那金矿控矿因素分析   总被引：1，自引：0，他引：1  

寸伟才  王绍明  涂国府 《云南地质》2011,30(3):265-268

安那金矿赋存于中泥盆统坡折落组硅质岩夹薄层状灰岩中。东西向安那不对称褶皱构造是主要控岩控矿构造,次级北东向断裂和层间断裂是矿区的储（容）矿构造;矿区的金矿化与基性岩浆活动关系密切。  相似文献   

北阿尔金地区古元古代ca.2.0Ga岩浆-变质事件   总被引：4，自引：3，他引：1  

朱文斌  葛荣峰  吴海林 《岩石学报》2018,34(4):1175-1190

中国有三个主要的克拉通,分别是华北、华南和塔里木,它们在显生宙经造山过程聚集到一起。塔里木克拉通位于中国的西北部,面积超过60万平方千米,其北侧为中亚造山带,南侧为西昆仑造山带和阿尔金造山带。塔里木克拉通的前寒武纪岩石主要出露在其南北两侧边缘,包括库鲁克塔格、敦煌、阿尔金、铁克里克和阿克苏地块,它们记录了塔里木克拉通早期的构造演化。北阿尔金地块的阿克塔什塔格地区位于塔里木克拉通的东南边缘。该地区最老的岩石被称为米兰群或阿克塔什塔格杂岩。主要岩石包括太古宙的TTG岩石和表壳岩,以及古元古代的片麻状花岗岩,另有少量变质基性岩呈包体状出露在强变形的长英质侵入体中。本文对该区闪长质片麻岩开展了锆石SHRIMP U-Pb定年,同时还对变质基性岩进行了锆石LA-ICP-MS U-Pb测年和地球化学分析,目的是要约束北阿尔金地区古元古代的岩浆-变质事件。闪长质片麻岩的结晶年龄为2.04～2.03Ga,它们形成于岛弧环境。地球化学分析表明,变质基性岩的原岩是拉斑玄武岩。它们有类似于E-MORB的平坦的稀土配分模式,Nb、Ta、Zr、Hf不亏损,说明它们形成于大洋板内环境。在变质基性岩中还识别出两期变质锆石,其中2.05～2.01Ga的早期锆石代表了麻粒岩相的变质作用,而1.98～1.96Ga的晚期锆石可能与角闪岩相的退变质作用有关。无论该区岩浆作用还是变质作用都与约2.0Ga发生的俯冲增生造山事件有关。  相似文献   

Early Mesozoic metamorphism and tectonic significance of the eastern segment of the Lhasa terrane,south Tibet     

《Journal of Asian Earth Sciences》2013

The metamorphic belt in the Basongco area, the eastern segment of Lhasa terrane, south Tibet, occurs as the tectonic blocks in Paleozoic sedimentary rocks. The Basongco metamorphic rocks are mainly composed of paragneiss and schist, with minor marble and orthogneiss, and considered previously to be the Precambrian basement of the Lhasa terrane. This study shows that the Basongco metamorphic belt experienced medium-pressure amphibolite-facies metamorphism under the conditions of T = 640–705 °C and P = 6.0–8.0 kbar. The inherited detrital zircon of the metasedimentary rocks yielded widely variable ²⁰⁶Pb/²³⁸U ages ranging from 3105 Ma to 500 Ma, with two main age populations at 1150 Ma and 580 Ma. The magmatic cores of zircons from the orthogneiss constrain the protolith age as ca. 203 Ma. The metamorphic zircons from all rocks yielded the consistent metamorphic ages of 192–204 Ma. The magmatic cores of zircons in the orthogneiss yielded old Hf model ages (T_DM2 = 1.5–2.1 Ga). The magmatic zircons from the mylonitized granite yielded a crystallization age of ca. 198 Ma. These results indicate that the high-grade metamorphic rocks from the Basongco area were formed at early Jurassic and associated with coeval magmatism derived from the thickening crust. The Basongco metamorphic belt, together with the western and coeval Sumdo and Nyainqentanglha metamorphic belts, formed a 400-km-long tectonic unit, indicating that the central segment of the Lhasa terrane experienced the late Paleozoic to early Mesozoic collisional orogeny.  相似文献   

http://www.sciencedirect.com/science/article/pii/S1674987112000679     

J.D.A.Piper 《地学前缘(英文版)》2013,4(1):7-36

Quasi-integrity of continental crust between Mid-Archaean and Ediacaran times is demonstrated by conformity of palaeomagnetic poles to near-static positions between～2.7-2.2 Ca,～1.5-1.2 Ga and～0.75-0.6 Ga.Intervening data accord to coherent APW loops turning at "hairpins" focused near a continental-centric location.Although peripheral adjustments occurred during Early Proterozoic （～2.2 Ga） and Grenville（～1.1 Ga） times,the crust retained a low order symmetrical crescent-shaped form constrained to a single global hemisphere until break-up in Ediacaran times.Conformity of palaeomagnetic data to specific Eulerian parameters enables definition of a master Precambrian APW path used to estimate the root mean square velocity(v_RMS) of continental crust between 2.8 and 0.6 Ga.A long interval of little polar movement between～2.7 and 2.2 Ga correlates with global magmatic shutdown between～2.45 and 2.2 Ga,whilst this interval and later slowdown at～0.75-0.6 Ga to velocities of <2 cm/year correlate with episodes of widespread glaciation implying that these prolonged climatic anomalies had an internal origin;the reduced input of volcanically-derived atmospheric greenhouse gases is inferred to have permitted freeze-over conditions with active ice sheets extending into equatorial latitudes as established by low magnetic inclinations in glaciogenic deposits.v_RMS variations through Precambrian times correspond to the distribution of U-Pb ages in orogenic granitoids and detrital zircons and demonstrate that mobility of continental crust has been closely related to crustal tectonism and incrementation.Both periods of near-stillstand were followed by rapid v_RMS recording massive heat release from beneath the continental lid at～2.2 and 0.6 Ga.The first coincided with the Lomagundi-Jatuli isotopic event and led to prolonged orogenesis accompanied by continental flooding and reconfiguration of the crust on the Earth’s surface;the second led to continental break-up and instigated the comprehensive Plate Tectonics that has characterised Phanerozoic times.The Mesoproterozoic interval characterised by anorogenic magmatism correlates with low v_RMS between～1.5 and 1.1 Ga.Insulation of the sub-continental mantle evidently permitted high temperature melting and weakening of the crustal lid to enable buoyant emplacement of large plutons at high crustal levels during this magmatic event unique to Mesoproterozoic and early Neoproterozoic times.  相似文献   

西太平洋典型边缘海盆的岩浆活动   总被引：1，自引：0，他引：1  

石学法  鄢全树 《地球科学进展》2013,28(7):737-750

在发育有全球最大、最复杂的弧—沟—盆体系的西太平洋地区,集中了全球75％左右的边缘海盆(弧后盆地).根据磁异常条带年龄,这些边缘海盆可粗略分为3个扩张幕.主要根据DS-DP,ODP和IODP计划实施以来所获得的成果,结合其他海洋调查航次研究成果,系统阐述了分属3个扩张幕的西菲律宾海盆(第一扩张幕)、南海—四国海盆(第二扩张幕)和冲绳海槽(第三扩张幕)—马里亚纳海槽内的岩浆活动特点.西菲律宾海盆(扩张时代为65～35 Ma BP)从原先的赤道位置迁移至现今的位置,其内存在如似正常洋中脊玄武岩(NMORB)、洋岛玄武岩(OIB)及弧火山岩等多种岩石类型,其地球动力学背景分别与弧后扩张、地幔柱及火山弧等背景有关,其复杂的构造演化样式需要进一步研究;四国海盆(扩张时代为27 ～ 15 Ma BP)是由古伊豆—小笠原—马里亚纳弧(IBM)裂解形成的,其内除发育正常(N)—富集(E)的洋中脊玄武岩(NMORB-EMORB)外,还在扩张停止的同时出现了板内火山作用,形成了中K-超K碱性玄武岩.四国海盆的扩张模式并没有从岩石学和地质年代学角度进行明确制约,板内火山作用的地球动力学背景也不甚清楚.南海(扩张时代为32～15.5 MaBP)是由来自华南地块的一些微陆块向东南裂离后的海底扩张所形成,并在海底扩张后2 ～8 Ma出现板内火山作用,截止目前,并没有获取到洋壳基底样品,主要获取到了南海海山似OIB的玄武岩,未来需要从岩石学和地质年代学角度对南海海底扩张动力学和时代以及扩张期后的板内火山作用动力学背景进行进一步制约.马里亚纳海槽(扩张时代为5 Ma BP至今)为一年青的洋内弧后盆地,其北段处于裂解增进阶段,其内出露有似MORB(中南段)及介于似MORB与似岛弧岩石之间过渡类型的玄武岩(增进端);虽然在扩张时代上与马里亚纳海槽相当,但冲绳海槽(扩张时代为4 Ma BP至今)为一陆缘、初生弧后盆地,从西南往东北方向,不同区段处于不同的伸展发育阶段,西南段出露有似MORB岩石,中段岩石主要为玄武质岩石和流纹质岩石组成双峰组合,而东北段为中酸性火山岩.正在活动的马里亚纳海槽与冲绳海槽的岩浆作用研究应和其伴随的火山岛弧及其相邻的海沟处正在俯冲的洋壳板块结合起来,完整理解板块俯冲输入(subduction input)与弧及弧后输出(volcanic output)之间的关系,这将为揭示西太平洋地区构造演化提供重要证据.即将在西太平洋地区实施的IODP 349 ～ 352航次,为我国科学家提供了研究西太平洋地区构造演化的契机.  相似文献   

安徽蚌埠西贾庄铅锌金银矿床赋矿地层和岩浆岩年代学、Hf同位素、地球化学特征及其意义   总被引：1，自引：0，他引：1  

陈杨  范裕  刘一男  王彪  刘青 《岩石学报》2019,35(12):3763-3781

安徽省北部蚌埠隆起位于华北克拉通东南缘,郯庐断裂带西侧。蚌埠隆起和胶东金矿区现今位置被认为是郯庐断裂带大规模左行平移引起,推测两区有相似的成矿背景。蚌埠隆起东西向长约160km,以固镇-永平岗断裂为界分为东西两段。前人已对蚌埠隆起东段的成岩成矿作用开展了元素地球化学和成矿流体等方面的研究,而蚌埠隆起西段由于第四系覆盖,一直未发现岩浆岩和相关成矿作用,被认为是无矿区,未有相关研究。西贾庄矿床是近年来蚌埠隆起西段新发现的矽卡岩型铅锌金银矿床,为区内成岩成矿作用研究提供了良好的对象。本次工作在矿床地质特征研究基础上,系统开展了矿床赋矿地层和岩浆岩的年代学、地球化学和Hf同位素的研究,确定了成矿岩体的源区、性质和演化,丰富和完善了区内成岩成矿作用研究。西贾庄矿床的赋矿地层为黑云母斜长片麻岩,成岩时代为2466±12Ma,确定其为五河群西堌堆组地层,其原岩来自2. 65～2. 85Ga新生地壳的重熔;花岗闪长斑岩为成矿岩体,成岩时代为113. 0±1. 0Ma～114. 9±1. 7Ma,石英二长岩为成矿期后脉岩,成岩时代为112. 1±0. 8Ma,因此限定成矿时代约为112～115Ma。花岗闪长斑岩和石英二长岩的地球化学特征基本相同,均属高钾钙碱性、准铝质-弱过铝质的Ⅰ型花岗岩类。这两类侵入岩的ε_(Hf)(t)=-16. 6～-12. 5,t_(DM2)=1963～2264Ma,表明它们的岩浆源区为老地壳(主要为古元古代)的部分熔融,推测其形成于古太平洋板块俯冲作用下的弧后伸展环境。通过对比,西贾庄矿床侵入岩与蚌埠隆起东段早白垩世晚期侵入岩体具有相同的构造背景和源区,蚌埠隆起西段在覆盖层之下仍有一定的成矿潜力。  相似文献   

Geochronology and geochemistry of early Paleozoic granitic and coeval mafic rocks from the Tannuola terrane (Tuva,Russia): Implications for transition from a subduction to post-collisional setting in the northern part of the Central Asian Orogenic Belt     

《Gondwana Research》2024

Early Paleozoic magmatism of the Tannuola terrane located in the northern Central Asian Orogenic Belt is important to understanding the transition from subduction to post-collision settings. In this study, we report in situ zircon U-Pb ages, whole rock geochemistry, and Sr-Nd isotopic data from the mafic and granitic rocks of the eastern Tannuola terrane to better characterize their petrogenesis and to investigate changing of the tectonic setting and geodynamic evolution. Zircon U-Pb ages reveal three magmatic episodes for about 60 Ma from ∼510 to ∼450 Ma, that can be divided into the late Cambrian (∼510–490 Ma), the Early Ordovician (∼480–470 Ma) and the Middle-Late Ordovician (∼460–450 Ma) stages. The late Cambrian episode emplaced the mafic, intermediate and granitic rocks with volcanic arc affinity. The late Cambrian mafic rocks of the Tannuola terrane may originate from melting of mantle source that contain asthenosphere and subarc enriched mantle metasomatized by melts derived from sinking oceanic slab. Geochemical and isotopic compositions indicate the late Cambrian intermediate-granitic rocks are most consistent with an origin from a mixed source including fractionation of mantle-derived magmas and crustal-derived components. The Early Ordovician episode reveal bimodal intrusions containing mafic rocks and adakite-like granitic rocks implying the transition from a thinner to a thicker lower crust. The Early Ordovician mafic rocks are formed as a result of high degree melting of mantle source including dominantly depleted mantle and subordinate mantle metasomatized by fluid components while coeval granitic rocks were derived from partial melting of the high Sr/Y mafic rocks. The latest Middle-Late Ordovician magmatic episode emplaced high-K calc-alkaline ferroan granitic rocks that were formed through the partial melting the juvenile Neoproterozoic sources.These three episodes of magmatism identified in the eastern Tannuola terrane are interpreted as reflecting the transition from subduction to post-collision settings during the early Paleozoic. The emplacement of voluminous magmatic rocks was induced by several stages of asthenospheric upwelling in various geodynamic settings. The late Cambrian episode of magmatism was triggered by the slab break-off while subsequent Early Ordovician episode followed the switch to a collisional setting with thickening of the lower crust and the intrusion of mantle-induced bimodal magmatism. During the post-collisional stage, the large-scale lithospheric delamination provides the magma generation for the Middle-Late Ordovician granitic rocks.  相似文献   

U-Pb and Pb-Pb zircon dating of the older orthogneiss suite in the Silvretta nappe,eastern Alps: Cadomian magmatism in the upper Austro-Alpine realm     

Bernhard Müller  Urs Stefan Klötzli  Markus Flisch 《International Journal of Earth Sciences》1995,84(3):457-465

Two orthogneiss suites dominate the Silvretta nappe. Primary crystallization of the larger suite (younger orthogneisses) is assumed to be Ordovician in age. The second, adjacent magmatic suite consists of older, alkaline to calc-alkaline, ultrabasic, basic to intermediate and granitic rocks known as older orthogneisses. U-Pb data of multigrain zircon fractions, as well as single zircon stepwise evaporation ²⁰⁷Pb/²⁰⁶Pb results suggest a latest Proterozoic to early Cambrian intrusion age for the protoliths of the older orthogneisses as both dating methods yield early Cambrian crystallization ages of 526±7 and 519±7 Ma for an alkaline granite gneiss; similar results were obtained for two neighbouring calc-alkaline orthogneisses (²⁰⁷Pb/²⁰⁶Pb ages of 533 ± 4 and 568 ± 6 Ma, respectively). The crystal habitus corresponds to P5, S19 and S9 zircons of magmatic origin. Whole-rock initial Sr isotope ratios indicate a primitive source. The igneous protoliths of these older orthogneisses represent a fragment of a Cadomian (Pan-African) crust found in places within the basement of the European Hercynides.  相似文献   

Rift propagation at craton margin.: Distribution of faulting and volcanism in the North Tanzanian Divergence (East Africa) during Neogene times   总被引：1，自引：0，他引：1  

B. Le Gall  P. Nonnotte  J. Rolet  M. Benoit  H. Guillou  M. Mousseau-Nonnotte  J. Albaric  J. Deverchre 《Tectonophysics》2008,448(1-4):1-19

A revised kinematic model is proposed for the Neogene tectono-magmatic development of the North Tanzanian Divergence where the axial valley in S Kenya splits southwards into a wide diverging pattern of block faulting in association with the disappearance of volcanism. Propagation of rifting along the S Kenya proto-rift during the last 8 Ma is first assumed to have operated by linkage of discrete magmatic cells as far S as the Ngorongoro–Kilimanjaro transverse volcanic belt that follows the margin of cratonic blocks in N Tanzania. Strain is believed to have nucleated throughout the thermally-weakened lithosphere in the transverse volcanic belt that might have later linked the S Kenya and N Tanzania rift segments with marked structural changes along-strike. The North Tanzanian Divergence is now regarded as a two-armed rift pattern involving: (1) a wide domain of tilted fault blocks to the W (Mbulu) that encompasses the Eyasi and Manyara fault systems, in direct continuation with the Natron northern trough. The reactivation of basement fabrics in the cold and intact Precambrian lithosphere in the Mbulu domain resulted in an oblique rift pattern that contrasts with the orthogonal extension that prevailed in the Magadi–Natron trough above a more attenuated lithosphere. (2) To the E, the Pangani horst-like range is thought to be a younger (< 1 Ma) structure that formed in response to the relocation of extension S of the Kilimanjaro magmatic center. A significant contrast in the mechanical behaviour of the stretched lithosphere in the North Tanzanian diverging rift is assumed to have occurred on both sides of the Masai cratonic block with a mid-crustal decoupling level to the W where asymmetrical fault-basin patterns are dominant (Magadi–Natron and Mbulu), whereas a component of dynamical uplift is suspected to have caused the topographic elevation of the Pangani range in relation with possible far-travelled mantle melts produced at depth further N.  相似文献   

华北地区晚中生代重大构造转折的地质证据   总被引：9，自引：3，他引：6  

陈根文夏 换  陈绍清 《中国地质》2008,35(6):1162-1177

华北地区在侏罗纪和白垩纪分别发生了两次不同性质的岩浆活动,早期形成一套高锶石英闪长岩,另一期为钾玄岩系。两套岩石分别代表地壳加厚和减薄的构造背景,两次岩浆活动的转折期大致在130Ma左右,此外,华北地区自垩纪广泛分布的碱性岩同样表明区域内在白垩纪曾发生过强烈的岩石圈伸展作用。这一地质特征与区内盆地地震剖面、造山带构造活动年龄、变质核杂岩的年龄、早向坚世太平洋板块运动方向和运动速率的改变以及郯庐断裂左旋运动年龄等地质资料相佐证。因此华北地区岩石圈减薄作用主要发生在早向垩世时期,晚侏罗世——早白垩世是华北地区中生代重大构造发生的转折点。  相似文献