贵州遵义早寒武黑色岩系底部Se的超常富集   总被引：14，自引：3，他引：11  

罗泰义  宁兴贤  罗远良  李晓彪  凌荣祥  姚林波 《矿物学报》2005,25(3):275-282

对遵义松林下寒武统牛蹄塘组黑色岩系部分样品的对比分析表明,应用不同光度法测定的硒和应用ICP-MS分析的硒之间存在良好的相关性,表明应用ICP-MS可以快速批量分析黑色岩系样品中的硒,提出用于推导硒含量的经验公式。利用该经验公式对遵义松林牛蹄塘组黑色岩系底部钾质斑脱岩段和中部镍钼金属层段的硒进行了计算,表明在这两个岩性段存在硒的超常富集,局部都达到了工业品位。钾质斑脱岩中硒与铜具有良好的相关性,表明硒可能存在于含铜硫化物中;在镍钼层中硒与镍、铜具有较好的相关性,表明硒主要存在于镍和铜的硫化物中。根据硒的亲硫性,进一步揭示了遵义钾质斑脱岩的原始岩浆可能为含黝方石和（或）钙霞石的粗安岩、粗面岩、响岩;在镍钼富集层中铜镍、铜硒及镍硒之间都具有良好的相关性,表明镍、铜、硒富集的原始物源与超基性岩浆铜镍硫化物的分离富集有关;根据钾质斑脱岩层与多金属富集层的空间相关性及微量元素组合特征．认为在遵义松林地区早寒武世时期深部存在碱性-超基性岩浆活动。  相似文献   

西藏冈底斯地块中新生代中酸性侵入岩浆活动与构造演化   总被引：4，自引：0，他引：4  

葛良胜  邓军  杨立强  邹依林  邢俊兵  袁士松  武玉海 《地质与资源》2006,15(1):1-10

冈底斯地块上的中新生代中酸性岩浆活动,是北部班公湖-怒江和南部雅鲁藏布两个特提斯演化及其后的陆内汇聚碰撞造山和后造山伸展等大地构造事件的完整记录.地块上的中酸性岩浆活动可划分为3个带,其中北部岩带岩浆岩形成于燕山期,其类型从早期的Ⅰ型到中期的过渡型演化为晚期的S型,分别形成于板块俯冲-缝合-碰撞等构造条件下,是北部班公湖-怒江特提斯演化的集中反映.中部和南部岩浆岩带则集中体现了雅鲁藏布特提斯时空演化的完整经历.其中,南部岩带岩体以燕山晚期为主,喜马拉雅早期次之,成因及形成环境与特提斯洋壳向北俯冲作用密切相关(燕山晚期),同时俯冲结束后的同碰撞条件下的岩浆活动在该岩带内也有明显的反映(喜马拉雅早期);中部岩带岩体以喜马拉雅早期为主,燕山晚期次之.岩体大部分为同碰撞环境下岩浆活动的产物,它表征了随着洋壳板块向北俯冲程度的加深和强度的加剧,岩浆活动中心在不断向北迁移,并最终缝合碰撞的过程.因此该岩带内岩浆岩主要形成于俯冲的晚阶段及缝合后的同碰撞条件下.喜马拉雅晚期的小斑岩体实际上广泛出露于整个冈底斯地块上,它反映的是该区在经历了碰撞造山后发生的陆内伸展的构造过程.  相似文献   

板块俯冲带岩浆作用过程的研究   总被引：1，自引：0，他引：1  

李怀明  翟世奎  陶春辉  于增慧  季敏 《海洋科学进展》2009,27(1)

综合分析了板块俯冲带岩浆活动的物质来源、岩浆上涌直至喷出的地球化学过程以及与这些过程相对应的时间尺度等研究的进展,指出了目前研究中存在的主要问题,并建议我国在该领域开展相关的研究中应:1)首先利用独有的地理优势,以处于弧后扩张作用早期的冲绳海槽为研究对象,开展相关的调查与研究;2)积极引进先进的技术手段;3)通过加强国际合作,积极参与国际合作项目,拓展研究领域.  相似文献   

蛇绿岩岩石组合及洋脊下岩浆作用   总被引：21，自引：0，他引：21  

张旗  钱青  王焰 《岩石矿物学杂志》2000,19(1):1-7

蛇绿岩的岩石组合从下至上分为４个单元,即：变质橄榄岩单元、深成杂岩单元、席状岩墙群杂岩单元和喷出岩单元。各单元的岩石组合是多种多样的：变质橄榄岩单元主要由方辉橄榄岩、二辉橄榄岩和少量纯橄岩及斜长二辉橄榄岩组成;深成杂岩单元单元包括辉长岩－镁铁质堆晶岩和超镁铁质堆晶岩,在深成杂岩和席状岩墙群杂岩单元内在复杂的岩浆侵入事件;喷出岩单元不仅仅由玄武岩组成,还包括安山岩、玻安岩、钠长岩以及乐砾岩、凝灰岩等  相似文献   

Petrology of basic and intermediate orogenic granitoids from the Sila Massif (Calabria,southern Italy)     

A. Caggianelli  A. Del Moro  G. Piccarreta 《Geological Journal》1994,29(1):11-28

Hercynian gabbroic, dioritic and tonalitic rocks crop out in the neighbourhood of Rovale (Sila Grande, Calabria). They make up a crude rectangular outcrop with the western part consisting of gabbroic rocks and the eastern of dioritic and tonalitic rocks. They come into contact with medium to high grade metapelites on the western side and with heterogeneous granodiorites on the other sides. In the gabbroic body both opx ± ol bearing cumulates and amphibole differentiates occur and are characterized by the widespread presence of brown pargasite. Sporadic magmatic to subsolidus corona textures between olivine and plagioclase or orthopyroxene and plagioclase can be observed and their preservation clearly suggests a post-tectonic emplacement for the gabbroic magma. Diorites and tonalites display hypidiomorphic textures free of olivine and orthopyroxene and bearing green Mg-hornblende. The granitoids, on the basis of chemical data, display orogenic features of the continent-continent collision type. The gabbroic rocks have high Al tholeiitic composition and fractionation of orthopyroxene and plagioclase played an important part in their evolution. The Rb/Sr isochron method did not give a precise emplacement age for the granitoids as a whole. Initial ⁸⁷Sr/⁸⁶Sr ratios (at 290 Ma) are higher in the gabbroic body (0.7091–0.7095) than in diorites and tonalites (0.7083–0.7092). Thus gabbroic rocks appear more displaced than diorites and tonalites towards crustal isotopic composition. The eNd data seem to confirm this feature, thus suggesting that the gabbroic rocks and diorites derived from distinct mantle magma batches. Interestingly, small isotropic gabbroic masses occur within the diorites and show general features that allow them to be considered as possibly parental with respect to the host diorites. The evolution to the dioritic composition might have occurred through fractionation and minor mixing with a more acidic component such as the northern granodiorites. Geochemical, Sr and Nd isotopic data indicate a scenario of a composite plutonic body formed by distinct magma batches of mixed crust and mantle origin.  相似文献   

Anatomy of the transpressional Dom Feliciano Belt and its pre-collisional isotopic (Sr–Nd) signatures: A contribution towards an integrated model for the Brasiliano/Pan-African orogenic cycle     

《Gondwana Research》2024

The Dom Feliciano Belt evolution is reviewed based on cross-sections, space–time diagrams, P-T paths, and Sr–Nd isotopic data of pre-collisional metaigneous rocks. The belt is divided into northern, central and southern sectors, subdivided into tectonic domains, developed at Neoproterozoic pre-, syn- and post-collisional stages. The northern sector foreland pre-collisional setting represents a rift, with tholeiitic (meta)volcanic rocks (∼800 Ma) chronocorrelated to hinterland intermediate and acidic orthogneisses of high-K calc-alkaline arc signature. In contrast, the central sector records a complete section from the forearc towards the back-arc region during pre-collisional times. In the western domain, ophiolites (∼920 Ma) are associated with arc-related orthogneisses and metavolcanic rocks (880–830 Ma; 760–730 Ma). At back-arc position, continental arc-related magmatism (800–780 Ma) is registered by hinterland orthogneisses and central foreland metavolcanic rocks. Ophiolites on the hinterland opposite side comprise two compositional groups, with N-MORB and supra subduction signature, interpreted as a back-arc basin record (∼750 Ma). The pre-Neoproterozoic basement of the whole belt is correlated with the Nico Perez Terrane and Luis Alves Block (Archean to Mesoproterozoic, with Congo Craton affinity). This contrasts with the Piedra Alta Terrane (Rio de La Plata Craton, only Paleoproterozoic), westernmost Uruguay. The suture between the Piedra Alta and Nico Perez terranes is correlated with the suture zone in the westernmost central sector. Transpression affected both foreland and hinterland during collision (660–640 Ma), with high-T/low-P hinterland progressive exhumation, whilst foreland low- to medium-grade correlated sequences record underthrusting. Post-collisional processes included magmatism throughout the belt (640–580 Ma), strain partitioning along strike-slip shear zones, and foreland basin fill. Late tectono-metamorphic and magmatic processes (560–540 Ma) were attributed to the Kalahari Craton collision. Arc magmatism migration due to subduction angle variations suggests modern-style plate tectonics during Gondwana amalgamation. Diachronism and kinematic inversion are characteristic of an oblique convergent multi-plate orogenic system.  相似文献   

义敦岛弧带弧后区板内岩浆作用的时代及意义   总被引：14，自引：0，他引：14  

曲晓明侯增谦  唐绍华 《岩石矿物学杂志》2003,22(2):131-137

通过对义敦岛弧夏囊沟一带酸性火山岩的岩石地球化学和Rb-Sr同位素研究,首次在该岛弧弧后区确立了一条板内火山岩带.这些火山岩属钾玄岩系列,以高K2O,低CaO,富Nb、Ta、Zr、Hf,贫Sr、Eu为特点,具标准的"V"型稀土元素配分型式,构造环境判别图解显示其形成于板内裂陷环境.由4个全岩样品给出的Rb-Sr等时线年龄t=189.2±5.0 Ma,相关系数R=0.999?824,ISr=0.714?578.认为火山岩的成分分异受斜长石在岩浆源区熔融残留和岩浆形成后黑云母的结晶分离双重控制.位于该带东侧弧后扩张盆地中的晚三叠世勉戈组双峰火山岩的形成年龄为213.1 Ma,说明该岛弧仅仅在24 Ma左右时限内就完成了从俯冲造弧到板内裂陷的重大转换,由此可对该岛弧带的碰撞造山过程和演化时序做出精确约束.  相似文献   

大陆弧岩浆幕式作用与地壳加厚:以藏南冈底斯弧为例   总被引：1，自引：0，他引：1  

马绪宣  许志琴  刘飞  赵中宝  李海兵 《地质学报》2021,95(1):107-123

大陆弧岩浆带位于汇聚板块的前缘,记录了洋陆俯冲过程和大陆地壳生长过程,是研究壳幔相互作用的天然实验室.越来越多的研究发现,大陆弧岩浆的生长与侵位并不是均一的、连续的过程,而是呈现阶段性、峰期性特征,即幕式岩浆作用.弧岩浆峰期与岩浆平静期相比,岩浆增生速率显著增强,易于发生岩浆聚集,继而形成大的岩基,如北美西部科迪勒拉造...  相似文献