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特提斯构造东南带的滇西南地区发育三个系列的晚古生代火山岩:碱性橄榄玄武岩系列,大陆拉斑玄武岩系列和类似MORB拉斑玄武岩系列。地质、地球化学特征反映它们可能是保山—掸邦地块东缘昌宁—孟连晚古生代裂谷(局部向初始洋盆转化),而不大可能是宽阔洋底和洋岛的火山作用产物。逐渐增强的前进式裂谷作用伴随陆壳的减薄(局部分离,洋壳诞生)和软流圈顶面的抬升,可能导致不同深度地幔产生不同程度熔融作用,形成本区三个系列岩浆。地幔对流可能引导陆缘裂谷、洋壳扩张、俯冲、微陆块碰撞以及岩石圈深部剪切作用,制约区域晚古生代至中生代早期的构造岩浆演化。 相似文献
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三江昌宁-孟连带原-古特提斯构造演化 总被引：4，自引：0，他引：4
昌宁-孟连特提斯洋的构造演化及其原特提斯与古特提斯的转换方式一直是青藏高原及邻区基础地质研究中最热门的科学问题之一.根据新的地质调查资料、研究成果并结合分析数据,系统总结了三江造山系不同构造单元地质特征,讨论了昌宁-孟连特提斯洋早古生代-晚古生代的构造演化历史.通过对不同构造单元时空结构的剖析和对相关岩浆、沉积及变质作用记录的分析,认为昌宁-孟连结合带内共存原特提斯与古特提斯洋壳残余,临沧-勐海一带发育一条早古生代岩浆弧带,前人所划基底岩系"澜沧岩群"应为昌宁-孟连特提斯洋东向俯冲消减形成的早古生代构造增生杂岩,滇西地区榴辉岩带很可能代表了俯冲增生杂岩带发生了深俯冲,由于弧-陆碰撞而迅速折返就位,这一系列新资料及新认识表明昌宁-孟连结合带所代表的特提斯洋在早古生代至晚古生代很可能是一个连续演化的大洋.在此基础上,结合区域地质资料,构建了三江造山系特提斯洋演化的时空格架及演化历史,认为其经历了早古生代原特提斯大洋扩张、早古生代中晚期-晚古生代特提斯俯冲消减与岛弧带形成、晚二叠世末-早三叠世主碰撞汇聚、晚三叠世晚碰撞造山与盆山转换等阶段. 相似文献
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大陆俯冲带通常是由大洋俯冲带发展而形成的,因而大陆造山带内通常会同时记录大洋俯冲和大陆俯冲阶段的信息。位于中国中东部的大别造山带记录了丰富的三叠纪华南、华北板块陆—陆碰撞信息,但几乎完全缺失晚古生代大洋俯冲阶段证据。基于古生代地质事件相关岩石可能被掩盖于合肥盆地底部或在大陆俯冲过程中被运移至地幔深部的推测,针对合肥盆地中部出露的玄武岩和辉绿岩开展了详细的锆石LA-ICP-MS U-Pb定年和Lu-Hf同位素分析。测试结果显示,大蜀山辉绿岩和小蜀山玄武岩均获得了较多的晚古生代年龄结果,加权平均年龄分别为338 Ma、270 Ma和349 Ma、273 Ma,鸡鸣山辉绿岩则主要表现为早白垩世年龄。这些基性岩浆岩中锆石年龄结果表现为连续分布的特征,2个最小的年龄结果指示了新生代基性岩浆活动的发生时间,其他锆石则来自于古老岩石的再循环。对高温条件下的锆石保存机制以及锆石来源的综合分析,可以得出合肥盆地基性岩中的晚古生代锆石来源于古特提斯洋俯冲形成的岩浆岩。三叠纪大陆俯冲阶段部分晚古生代岩浆岩被俯冲板片运移至地幔深部,而后在新生代太平洋板块俯冲过程中与深部地幔一起部分熔融而形成合肥盆地新生代基性... 相似文献
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大理海东地区,地处二叠纪峨眉山地幔柱活动形成的川滇黔接壤地区峨眉山大火成岩省之一的扬子陆块西缘盐源-丽江凹陷(火山岩)带南端。1华力西晚期岩浆活动受峨眉山地幔柱影响,引发扬子陆块内大规模超基性-基性岩浆的侵入与喷出。早阶段通常产生剧烈的深成爆发,形成爆发角砾岩筒、火山 相似文献
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西秦岭北缘早古生代天水—武山构造带及其构造演化 总被引：5，自引：1，他引：4
西秦岭北缘早古生代天水-武山构造带位于甘肃省东部天水地区,主要由寒武纪关子镇-武山蛇绿岩带、晚寒武世-早奥陶世李子园群浅变质活动陆缘沉积-火山岩系、奥陶纪草滩沟群岛弧型火山-沉积岩系以及加里东期岛弧型深成侵入岩体、俯冲-碰撞型花岗岩体等组成.关子镇蛇绿岩中变质基性火山岩属于N-MORB型玄武岩,武山蛇绿岩中变质基性火山岩属于E-MORB型玄武岩,是洋脊型蛇绿岩的重要组成部分,形成时代大致在534～489Ma之间的寒武纪.李子园群火山岩主要形成于岛弧或与岛弧相关的弧前盆地构造环境,草滩沟群火山岩形成于与俯冲作用相关的岛弧环境.关子镇流水沟和百花中基性岩浆杂岩总体形成于中晚奥陶世(471～440Ma)古岛弧构造环境,同时发育加里东期俯冲型(450～456Ma)花岗岩类和碰撞型(438～400Ma)花岗岩类岩浆活动.西秦岭北缘早古生代古洋陆构造格局经历了从洋盆形成-洋壳俯冲消减直至陆-陆碰撞造山的板块构造演化过程.总体构造演化可划分为四个阶段:①晚寒武世古洋盆初始形成阶段;②早奥陶世洋盆初始俯冲阶段;③中晚奥陶世洋壳大规模俯冲与古岛弧发育阶段;④志留纪陆-陆或陆-弧碰撞造山阶段. 相似文献
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南秦岭构造带内早古生代碱基性岩浆活动：古特提斯洋裂解的证据 总被引：2，自引：0，他引：2
位于南秦岭构造带南缘的勉略(勉县—略阳)洋是东古特提斯洋的北侧分支洋盆,在勉县—略阳地区发育有典型的蛇绿岩组合。然而,由于中三叠世晚期开始的碰撞造山作用以及之后陆内变形作用的改造,对于勉略洋盆在构造带东段的裂解和演化过程并不清晰。本文对发育于东南秦岭构造带内的基性岩墙群进行了岩石学、岩石地球化学、同位素年代学等方面的研究。结果表明,基性岩脉以辉长岩、辉绿岩等基性岩为主,其SiO 2含量为41.89%~49.75%,属基性—超基性岩类,并具有富钠、高钛的碱性岩特征。岩石的稀土、微量元素和Sr—Nd同位素特征与板内洋岛玄武岩(OIB)特征一致,岩浆源于具有地壳混染的板内洋岛玄武岩型地幔源区。该类基性岩脉顺层侵入到早古生代早期地层中,通过基性岩脉中的锆石SHRIMP测年获得岩脉顺层侵位的时代为晚志留世早期(约422 Ma)。这种岩浆作用很可能与古特提斯洋初始裂解有关,并导致南秦岭构造带内地壳伸展、基性岩浆侵位,该过程与南秦岭构造带北缘的商丹(商南—丹凤)原特提斯洋的消减和陆内俯冲可能相关。 相似文献
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秦祁结合部清水-张家川基性岩形成时代和构造归属探讨 总被引：1，自引：1，他引：0
中央造山系北缘发育完整的早古生代"弧-盆"体系,而其洋内弧盆体系还是陆缘弧盆体系属性的确定,可为原特提斯域古板块构造格局和中央造山系早期造山过程的恢复提供依据。秦岭-祁连结合部清水-张家川地区出露的与原特提斯洋俯冲作用相关的基性岩形成时代和构造归属的探究,是解决中央造山系早古生代洋-陆转换过程以及东西链接等科学问题的重要内容之一。清水-张家川地区主要出露块状、枕状玄武岩以及少量辉绿岩墙和硅质岩夹层,玄武岩和辉绿岩明显富集Th、LREE,亏损Nb、Ta、Zr、Hf和Ti元素,而Th/Nb比值则分为1. 09～2. 04和0. 18～0. 73两组,分别与岛弧和弧后裂谷熔岩相一致。另外,这些基性岩具较高的Th/Yb和εNd(t)(+4. 4～+4. 8)值,显示岩浆来自受洋壳沉积物混染的亏损地幔源区。最新LA-ICP-MS锆石U-Pb测年结果显示辉绿岩墙形成于500±3Ma。结合区域岩石地层资料,综合分析表明清水-张家川地区基性岩形成于寒武纪,早于晚奥陶世酸性火山岩和侵入岩。它们与其东、西侧北秦岭和北祁连构造带内的寒武纪-早奥陶世洋内弧和弧后盆地岩浆岩共同构成了原特提斯洋北缘早古生代洋内弧-盆体系。 相似文献
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俞 《四川地质科技情报》1994,(1):44-44
从早二叠世晚期开始，在古特提斯洋扩张影响下，扬子地块西缘发生了大陆伸展活动，形成一系列的裂陪盆地。三叠纪这一地区的裂陪活动增强，形成一些与之有亲缘关系的陆块。陆块问普遍发育有基性、超基性岩浆岩和水下喷发的枕状熔岩，见有放射虫硅质岩，出现滑塌堆积、碳酸盐重力流及陆源碎屑浊积岩，并有局部小型洋壳形成。以西部金沙江、甘孜-理塘的扩张规模较大， 相似文献
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QIU Ruizhao CHEN Yuming CHEN Xiuf ZHAO Hongjun REN Xiaodong ZHAO Like ZHANG Cao WANG Liangliang 《《地质学报》英文版》2019,93(Z2):43-44
The Paleo‐Tethys Ocean was a Paleozoic ocean located between the Gondwana and Laurasia supercontinents. It was usually consider to opening in the early Paleozoic with the rifting of the Hun superterrane from Gondwana following the subduction of the Rheic Ocean/proto‐Tethys Ocean. However, the opening time and detailed evolutionary history of the Paleo‐Tethys Ocean are still unclear. The Paleozoic ophiolites have recently been documented in the middle of the Qiangtang terrane, northern Tibetan Plateau, and they mainly occur in the Gangma Co area. These ophiolites are composed of serpentinite, pyroxenite, isotropic and cumulate gabbros, basalt, hornblendite and plagiogranite. Whole‐rock geochemical data suggest that all mafic rocks were formed in an oceanic‐ridge setting. Furthermore, positive whole‐rock εNd(t) and zircon εHf(t) values suggest that these rocks were derived from a long‐term depleted mantle source. The data allow us to conform that these rocks represent an ophiolite suite. Zircon U‐Pb dating of gabbros and plagiogranites yielded weighted mean ages of 437‐501 Ma. The occurrence of the ophiolite suite suggests that a Paleozoic Ocean basin (Paleo‐Tethys) existed in middle of the Qiangtang terrane. We hypothesize that the ophiolite in the middle of the Qiangtang terrane represents the western extension of the Sanjiang Paleo‐Tethys ophiolite in the east margin of the Tibetan Plateau, and they mark the main Paleo‐Tethys Ocean. This is the oldest ophiolite from the Paleo‐Tethyan suture zones and the Paleo‐Tethys Ocean basin probably opened in the Middle Cambrian, and continued to grow throughout the Paleozoic. The ocean was finally closed in the Middle to Late Triassic as inferred from the metamorphic ages of eclogite and blueschist that occur nearby. The Paleo‐Tethys Ocean was probably formed by the breakup of the northern margin of Gondwana, with southward subduction of the proto‐Tethys oceanic lithosphere along the northern margin of the supercontinent. 相似文献
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内蒙古贺根山蛇绿岩形成时代及构造启示 总被引：16，自引：5，他引：11
贺根山蛇绿岩位于兴蒙造山带北缘,发育完整的地幔橄榄岩、堆晶岩和基性熔岩组合,伴生有放射虫硅质岩,但贺根山蛇绿岩的形成时代一直存在争议,给兴蒙造山带北部构造演化阶段划分造成了很大障碍。锆石U-Pb年代学研究表明,贺根山蛇绿岩中辉长闪长岩(341±3Ma)和玄武岩(359±5Ma)结晶年龄为早石炭世早期,同时玄武岩继承锆石峰值年龄为晚泥盆世早期(375±2Ma),这些继承锆石呈短柱状、棱角状,生长环带宽缓,多为补丁状、平坦状,为典型的基性岩浆锆石,表明最迟在晚泥盆世早期洋壳物质已经开始形成。上石炭统格根敖包组火山岩与蛇绿岩局部呈喷发不整合接触,该组的晶屑凝灰岩夹层时代为晚石炭世(323±3Ma),提供了蛇绿岩构造侵位年龄的上限。因此,将贺根山蛇绿岩形成时代定为晚泥盆世-早石炭世,侵位时代为晚石炭世。侵入地幔橄榄岩中的部分基性岩脉时代为早白垩世(132±1Ma、139±3Ma和120±1Ma),它们含有大量继承锆石(144±1Ma~2698±25Ma),继承锆石峰值年龄密切响应了兴蒙造山带北部早白垩世之前复杂的岩浆及构造事件,这些基性岩脉是燕山期伸展环境下的岩浆产物,并非早白垩世蛇绿岩。结合前人的工作成果和区域岩浆岩、地层时空分布特征,建立了兴蒙造山带北部晚古生代构造演化历程:二连贺根山一线早泥盆世处于剥蚀阶段,中泥盆世陆壳拉张出现新生洋盆,晚泥盆世早期洋盆持续扩张形成新生洋壳,早石炭世晚期洋壳开始向北俯冲消减,并持续增生至西伯利亚活动陆缘,晚石炭世洋盆陆续闭合,部分已经构造侵位的蛇绿岩被晚石炭世火山岩不整合覆盖,贺根山蛇绿岩正是该洋盆的残余产物。 相似文献
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浅变质岩在示踪大别—苏鲁造山带大陆板块俯冲与折返过程中的意义 总被引：3，自引：0，他引：3
中国大别-苏鲁造山带为大陆板块俯冲形成的碰撞造山带,该带北缘和内部产有原岩时代为新元古代-晚古生代的浅变质岩。这些浅变质岩对应于扬子板块北缘前寒武变质基底和扬子板块北缘古生代大陆架沉积物,形成过程于印支期扬子板块向北俯冲过程中的刮削作用密切相关,与大洋板块俯冲过程中刮削形成的加积楔具有类似的动力学过程。对大别-苏鲁造山带浅变质岩的深入研究,不仅有助于揭示大陆板块俯冲过程中高压-超高压岩石形成与折返过程,而且确定了扬子板块与华北板块之间的缝合线位置位于大别造山带北淮阳带的北部和苏鲁造山带的五莲-蓬莱群的北侧。 相似文献
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The Late Paleozoic magmatism in central Inner Mongolia provides important insights on the tectonic evolution and crustal growth in the Central Asian Orogenic Belt (CAOB), which formed due to the closure of the Paleo-Asian Ocean (PAO). This paper presents new zircon UPb ages and Hf isotopic compositions as well as whole-rock geochemical data on a suite of volcanic rocks from the Late Paleozoic Baoligaomiao Formation and coeval intrusions in the Baiyinwula region of the Mongolian Arc. This study revealed that the magmatic sequences evolution includes: (1) early andesites (317–311 Ma) with enrichment in large ion lithophile elements (LILEs), depletion in high field strength elements (HSFEs), and positive zircon εHf (t) values from +9.0 to +15.5, indicating a derivation from enriched mantle; (2) felsic rocks emplaced from 306 Ma to 292 Ma, with relatively lower εHf (t) values from +6.3 to +11.3, implying juvenile crust as the primary magma source; and (3) A-type igneous rocks (280–278 Ma). The comparison of palaeontological, lithostratigraphical, and magmatic evolution in Late Paleozoic between different tectonic units in the eastern part of CAOB has displayed that the subduction of Paleo-Asian oceanic crust caused the opening of the Hegenshan Ocean along the southern margin of Mongolian Arc in Devonian; and the Baoligaomiao Formation volcanic rocks and coeval intrusions have recorded early northwards subduction and subsequent slab rollback of Hegenshan oceanic crust. 相似文献
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冀东晚古生代东湾子岩体的岩石成因研究 总被引：5，自引：3，他引：2
冀东晚古生代东湾子岩体由角闪石岩、少量辉石岩和辉长岩组成.典型的堆晶结构、全岩和镁铁质矿物(透辉石、角闪石)的上凸型稀土分布模式、相容元素含量低且变化范围大(如:角闪石岩中V=296×10-6～673×10-6)的特征表明了岩体的堆晶成因.计算得到的与辉石岩中的透辉石相平衡的熔体具有很高的稀土含量,轻重稀土分馏较为明显,富集大离子亲石元素(如:Sr,Ba,K),亏损高场强元素(如:Nh,Zr,Ti),具有典型的弧岩浆特征.透辉石和角闪石的矿物成分也具有弧岩浆的特征.高钙透辉石、大量的角闪石与黑云母的存在说明母岩浆富水.透辉石在高PH2O的状态下与熔体反应,生成角闪石的结构特征也证明了这一点.结合岩体的球化学特征,认为岩浆来源于富集的含有角闪石的尖晶石橄榄岩的部分熔融,母岩浆具有富水的特征(>3%).考虑到岩体形成时代(～300Ma;Zhao et al.,2007)和地质背景,认为东湾子岩体与位于华北北缘的其它晚石炭-早二叠世的岩体形成于同一构造背景下,都是晚古生代时期古亚洲洋向华北板块之下俯冲的产物. 相似文献
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Hossein Azizi Ayten Hadi Yoshihiro Asahara Youssef Osman Mohammad 《Central European Journal of Geosciences》2013,5(4):523-537
The Iraqi Zagros Orogenic Belt includes two separate ophiolite belts, which extend along a northwest-southeast trend near the Iranian border. The outer belt shows ophiolite sequences and originated in the oceanic ridge or supra-subduction zone. The inner belt includes the Mawat complex, which is parallel to the outer belt and is separated by the Biston Avoraman block. The Mawat complex with zoning structures includes sedimentary rocks with mafic interbedded lava and tuff, and thick mafic and ultramafic rocks. This complex does not show a typical ophiolite sequences such as those in Penjween and Bulfat. The Mawat complex shows evidence of dynamic deformation during the Late Cretaceous. Geochemical data suggest that basic rocks have high MgO and are significantly depleted in LREE relative to HREE. In addition they show positive ? Nd values (+5 to+8) and low 87Sr/86Sr ratios. The occurrence of some OIB type rocks, high Mg basaltic rocks and some intermediate compositions between these two indicate the evolution of the Mawat complex from primary and depleted source mantle. The absence of a typical ophiolite sequence and the presence of good compatibility of the source magma with magma extracted from the mantle plume suggests that a mantle plume from the D″ layer is more consistent as the source of this complex than the oceanic ridge or supra-subduction zone settings. Based on our proposed model the Mawat basin represents an extensional basin formed during the Late Paleozoic to younger along the Arabian passive margin oriented parallel to the Neo-Tethys oceanic ridge or spreading center. The Mawat extensional basin formed without creation of new oceanic basement. During the extension, huge volumes of mafic lava were intruded into this basin. This basin was squeezed between the Arabian Plate and Biston Avoraman block during the Late Cretaceous. 相似文献
17.
The Carboniferous volcanic rocks in western Hainan Island consist of a series of oceanic tholeite and rhyoporphyrite,showing bimodal nature.Similar geochemical characters,in terms of abun-daces and relative rations of incompatible elements and REE and the REE patterns,between the basalt and continental rift-associated tholeiite indicate the occurrence of Late Paleozoic rifting in the area.The basaltic magma,with a low degree of evolution,was originated from deep mantle,show-ing contamination by low crustal material.The rhyolite is thought to be formed from partial melting of the continental crust by higher thermal flow in a rift environment rather than from fractional crystallization of a basaltic magma. 相似文献
18.
西准噶尔石炭纪洋中脊俯冲岩浆活动:以玛里雅蛇绿岩为例 总被引：4，自引：2，他引：2
玛里雅蛇绿岩位于新疆准噶尔西缘达拉布特断裂东侧的弧前增生楔内,形成于石炭纪,出露岩石类型齐全,其中硅质岩与火山岩相间出露,多表现为非构造接触。地球化学特征表明,它们大致可以分为四个系列:(1)A系列为岛弧英安岩,Th强烈富集,可能有洋壳沉积物参与,高场强元素Nb亏损,与洋壳的俯冲有关;(2)M系列与典型洋中脊玄武岩的稀土元素配分模式一致,不过Ba强烈富集,可能受到俯冲流体的影响;(3)E系列位于地幔序列N-MORB和E-MORB之间,表明它可能是地幔岩浆的混合产物,未受到地幔岩浆源区之外物质的影响;(4)O系列与典型的洋岛玄武岩基本一致,只是Ta、La和Th含量略偏低,但都处于地幔序列范围内,可能与其他岩浆源有轻微的混合。这种岩浆特征与智利洋中脊俯冲环境下所产生的岩浆特征一致;由于西准噶尔晚古生代仍然发生俯冲消减,因此推测玛里雅蛇绿岩可能形成于洋中脊俯冲环境。 相似文献
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20.
《International Geology Review》2012,54(11):1313-1339
ABSTRACTThe nature, magmatic evolution, and geodynamic setting of both inner and outer Makran ophiolites, in SE Iran, are enigmatic. Here, we report mineral chemistry, whole-rock geochemistry, and Sr–Nd–Pb isotope composition of mantle peridotites and igneous rocks from the Eastern Makran Ophiolite (EMO) to assess the origin and tectono-magmatic evolution of the Makran oceanic realm. The EMO includes mantle peridotites (both harzburgites and impregnated lherzolites), isotropic gabbros, diabase dikes, and basaltic to andesitic pillow and massive lava flows. The Late Cretaceous pelagic limestones are found as covers of lava flows and/or interlayers between them. All ophiolite components are somehow sheared and fragmented, probably in Cenozoic time, during the emplacement of ophiolite. This event has produced a considerable extent of tectonic melange. Tectonic slices of trachy-basaltic lavas with oceanic island basalt (OIB)-like signature seal the tectonic melange. Our new geochemical data indicate a magmatic evolution from fore-arc basalt (FAB) to island-arc tholeiite (IAT)-like signatures for the Late Cretaceous EMO lavas. EMO extrusive rocks have high εNd(t) (+8 to +8.9) and isotopically are similar to the Oman lavas. This isotopic signature indicates a depleted mid-ocean ridge basalt (MORB) mantle source for the genesis of these rocks, except isotopic gabbros containing lower εNd(t) (+5.1 to +5.7) and thus show higher contribution of subducted slab components in their mantle source. High 207Pb/204Pb and 208Pb/204Pb isotopic ratios for the EMO igneous rocks also suggest considerable involvement of slab-derived components into the mantle source of these rocks. The variable geochemical signatures of the EMO lavas are mostly similar to Zagros and Oman ophiolite magmatic rocks, although the Pb isotopic composition shows similarity to the isotopic characteristic of inner Zagros ophiolite belt. This study postulates that the EMO formed during the early stages of Neo-Tethyan subduction initiation beneath the Lut block in a proto-forearc basin. We suggest subduction initiation caused asthenospheric upwelling and thereafter melting to generate the MORB-like melts. This event left the harzburgitic residues and the MORB-like melts interacted with the surrounding peridotites to generate the impregnated lherzolites, which are quite abundant in the EMO. Therefore, these lherzolites formed due to the refertilization of mantle rocks through porous flows of MORB-like melts. The inception of subduction caused mantle wedge to be enriched slightly by the slab components. Melting of these metasomatized mantle generated isotropic gabbros and basaltic to andesitic lavas with FAB-like signature. At the later stage, higher contribution of the slab-derived components into the overlying mantle wedge causes formation of diabase dikes with supra-subduction zone – or IAT-like signatures. Trachy-basalts were probably the result of late-stage magmatism fed by the melts originated from an OIB source asthenospheric mantle due to slab break-off. This occurred after emplacement of EMO and the formation of tectonic melange. 相似文献