喀雅克登塔格地区古元古代金水口变质侵入岩(体)的发现及其地质意义   总被引：3，自引：0，他引：3  

张金明  王钦元  许海全  严玉峰 《西北地质》2012,(3):13-19

在喀雅克登塔格地区古元古代金水口群片麻岩、大理岩中,发现了一套变质侵入体。岩性为眼球状黑云二长片麻岩,经同位素年龄测定时代为新元古代,侵入体具有过铝钙碱性系列的特征,是同碰撞环境下岩浆作用产物。该套变质侵入岩的发现,对于东昆仑西段前震旦纪基底的深入研究及更进一步恢复和确定喀雅克登塔格构造岩浆带发展演化具有重要意义。  相似文献   

藏南古堆地区的新生代构造样式     

杨斌 《地质与勘探》2014,50(Z1):1314-1319

藏南古堆地区具南北分带特征。北部地区靠达拉岩体,受也拉香波穹窿影响,断层以倾向南的正断层为主,地层呈多期次挤压褶皱形态,且出现呈楔形构造夹片出露的红柱石板岩、石榴石片岩等变质核杂岩地层;中部地区断层、褶皱较发育,褶皱呈紧闭的层间同斜褶皱,断层以倾向北的叠瓦状脆-韧性逆冲断层为主;南部地区为相对稳定区,该区地层相对较完整,褶皱以宽缓向斜形式出现,且越往南越宽缓。这一构造样式是印度板块与欧亚板块碰撞之后,在喜马拉雅造山运动影响及后期伸展作用的背景之下,由北向南的挤压推覆的结果,总体上它是一套挤压褶皱～推覆逆冲断层的组合,呈叠瓦状展布的隆子断裂是主推覆断层。  相似文献   

Zircon U‐Pb/Lu‐Hf and monazite chemical dating of the Tirodi biotite gneiss: implication for latest Palaeoproterozoic to Early Mesoproterozoic orogenesis in the Central Indian Tectonic Zone     

Santanu Kumar Bhowmik  Simon A. Wilde  Anubha Bhandari 《Geological Journal》2011,46(6):574-596

In this investigation, we reconstruct the latest Palaeoproterozoic to Early Mesoproterozoic orogenic events along the southern margin of the Central Indian Tectonic Zone (CITZ), using sensitive high resolution ion microprobe (SHRIMP) U‐Pb zircon dating and Lu‐Hf isotope analyses of zircon and Th‐U‐Pb chemical dating of monazite from samples of the Tirodi biotite gneiss (TBG) unit in the Sausar Mobile Belt (SMB), the latter constituting the southernmost litho‐tectonic component of the CITZ. U‐Pb zircon dating of one migmatitic gneiss sample from the type locality of the Tirodi biotite gneiss in the northern domain of the SMB has yielded an age of 1618 ± 8 Ma, which is considered to be the time of magmatic crystallization of its protolith. Combined U‐Pb zircon and monazite chemical dating of two granite gneiss samples from the southern domain of the SMB broadly constrain magmatic crystallization between 1603 ± 23 Ma and 1584 ± 17 Ma and an overprinting metamorphic recrystallization event at 1572 ± 7 Ma. Monazites from the granite gneiss samples also record a terminal metamorphic event at 1415 ± 23 Ma. Lu‐Hf isotopic analyses of zircons reveal fundamentally different source rock reservoirs for the protoliths of these magmatic rocks across the SMB. While the type TBG from the northern domain was derived from an Early Palaeoproterozoic source T(Hf) from 2093 to 2523 Ma, with a mean value at 2379 Ma) of essentially juvenile material with minor crustal components (εHf(t) from −3.3 to + 3.7), the granite from the southern domain had a mature crustal source (εHf(t) from −12.5 to −21.9) of Palaeoarchaean age T(Hf) from 3051 to 3630 Ma, with a mean value at 3218 Ma). When integrated with metamorphic information previously obtained from the 1.6 Ga ultra‐high temperature granulite facies metamorphic event in the SMB, the discrete magmatic and metamorphic events between 1.62/1.60 Ga and 1.42 Ga can be correlated with the formation of an Early Mesoproterozoic accretionary orogen in the CITZ. Copyright © 2011 John Wiley & Sons, Ltd.  相似文献   

华南陆块陆内成矿作用的一些科学问题   总被引：21，自引：4，他引：17       下载免费PDF全文

胡瑞忠  毛景文  范蔚茗  华仁民  毕献武  钟宏  宋谢炎  陶琰 《地学前缘》2010,17(2):13

华南陆块由扬子地块和华夏地块组成,是全球罕见的世界级多金属成矿省,成矿潜力巨大。华南陆块的形成和演化,受到了很有特色的陆内大陆动力学过程的影响,其中的晚古生代地幔柱成矿系统、中生代大面积低温成矿系统、中生代大花岗岩省成矿系统等陆内成矿系统,在全球背景中很有特色,是全球研究陆内成矿作用的理想基地。对华南陆块地质历史时期的大陆动力学过程如何制约上述成矿作用的发生,以往已开展不同程度的研究并取得重要成果。笔者在论述这些研究进展的基础上,提出了三大成矿系统需要进一步研究的一些科学问题。  相似文献   

三江特提斯复合造山与成矿作用研究进展   总被引：69，自引：57，他引：12  

邓军  杨立强  王长明 《岩石学报》2011,27(9):2501-2509

国家973规划项目"三江特提斯复合造山与成矿作用"实施3年来,在成矿动力学背景、增生造山成矿系统、碰撞造山成矿系统、构造体制转换与复合叠加成矿作用、成矿预测理论和勘查技术集成等方面取得了重要进展。(1)厘定了原特提斯、古特提斯、新特提斯和陆陆碰撞等一系列重要的区域构造-岩浆事件及其动力学背景,提出存在较大规模的燕山期构造-岩浆-成矿事件。(2)划分了被动边缘盆地型、活动边缘多岛弧盆型和大洋盆地型3个VMS型Cu-Pb-Zn成矿子系统,确立了玉龙和格咱-香格里拉斑岩型Cu矿带印支期岩浆作用的贡献及俯冲岛弧构造环境。(3)沉积岩容矿Pb-Zn-Cu-Ag多金属矿床的形成贯穿于印-亚大陆碰撞的三个演化阶段,成矿年代由南向北逐渐变新;它包括2套子系统:脉状Cu成矿系统,与变质流体活动有关,成矿物质来自深部地壳和浅部沉积地层的混合;Pb-Zn(-Cu-Ag)成矿系统,与盆地流体活动有关,成矿物质主要来自沉积地层。(4)金沙江-哀牢山斑岩型Cu(Au)成矿系统形成于35Ma左右,受控于印-亚大陆碰撞导致的地壳增厚。(5)造山型Au成矿系统主要发育在哀牢山金矿带,三期金成矿作用发生于~62Ma、~35Ma和28Ma左右,分别受控于印-亚碰撞早期的强烈汇聚挤压、早-晚期转换构造动力学体制。(6)区域存在3期重要构造体制转换事件:增生造山→碰撞造山、主碰撞→晚碰撞和晚碰撞→后碰撞,前两者控制区域斑岩铜矿带、沉积岩容矿多金属矿带和造山型金矿带,后者控制了沱沱河盆地中的Pb-Zn矿床。(7)最典型的叠加成矿系统为VMS 型Cu-Pb-Zn与斑岩型Cu叠加成矿系统,主要发育于羊拉-红山-普朗-铜厂沟矿集区、云县-景谷、江达-维西和昌宁-孟连成矿带。(8)探索成矿预测理论与方法,并选择羊拉-红山-普朗-铜厂沟矿集区为重点地区,开展隐伏矿体预测工作,取得找矿进展。本专辑论文基本覆盖了上述各个方面的研究进展,论文涉及4个主题:成矿动力学背景、增生造山成矿系统、碰撞造山成矿系统、构造体制转换与复合叠加成矿作用。  相似文献   

大巴山前陆弧形构造的成因：来自砂箱实验的认识   总被引：1，自引：0，他引：1  

王瑞瑞  张岳桥  解国爱  许怀智 《地质学报》2011,85(9):1409-1419

基于砂箱实验方法,本文对大巴山前陆弧形构造的成因进行了探讨.实验结果表明,多种要素的共同作用造就了大巴山弧形构造的形成,这些要素包括:早期伸展背景下形成的弧形边界、两侧基底地块的砥柱作用、底部滑脱层等.此外,北大巴山早期的伸展构造对随后挤压背景下的构造组合可能具有重要的制约作用.结合前人研究,大巴山弧形构造的演化可分为...  相似文献   

Nearshore to offshore facies and depositional history of the Ordovician Daylesford Limestone New South Wales     

V. Semeniuk 《Australian Journal of Earth Sciences》2013,60(4):449-463

The Daylesford Limestone is the basal formation of the Ordovician Bowan Park Group of central western New South Wales. The formation contains four main limestone types and minor intercalated terrigenous beds. Limestones are: (1) grain‐stone, (2) grey skeletal wackestone and packstone, (3) dark grey burrowed wackestone and packstone, and (4) dark grey burrowed lime mudstone. Grainstone and grey skeletal wackstone and packstone are dominant in eastern sections; they are laterally equivalent to, and interfinger with, dark grey muddy limestones that dominate western sections. Lithoclasts are abundant in the grainstone but are absent from muddy sections to the west except in thin beds above disconformities. The rock types of the Daylesford Limestone also tend to occur sequentially above some disconformities; the full sequence is: grainstone (or grey skeletal wackestone and packstone) grading up into dark grey burrowed wackestone and packstone and thence into dark grey burrowed lime mudstone. Each sequence is probably trans‐gressive and reflects deepening water.

During deposition of the Daylesford Limestone, an area to the east was uplifted, providing lithoclasts to be reworked into the neighbouring depositional basin. Uplift also produced numerous regressions and subaerial disconformities. Facies patterns were essentially similar throughout the history of the formation. Grainstone accumulated in high‐energy nearshore environments adjacent to the uplifted area, and grey skeletal wackestone and packstone in low‐energy nearshore environments. Dark grey lime mudstone formed in offshore low‐energy environments to the west of the uplifted area; and dark grey wackestone and packstone in intermediate environments. In parts, burrowing organisms kept pace with sedimentation and locally mixed interbedded grainstone and muddy limestone.  相似文献   

Metamorphic consequences of Neogene thermal anomaly in the northern Apennines (Radicondoli-Travale area,Larderello geothermal field – Italy)     

Marilisa Carella  Paolo Fulignati  Giovanni Musumeci 《Geodinamica Acta》2013,26(6):345-366

Abstract

In the Radicondoli–Travale area of the Larderello geothermal field (Italy) new structural and petrologic data on some metamorphic units, cored from geothermal wells, reveal the existence of a wide complex of hornfels rocks. The development of the complex is related to the emplacement of Neogene magmatic rocks at a shallow depth within a Permo–Triassic terrigenous metasedimentary sequence of a low metamorphic grade. The sequence was subjected to alpine tectonic-metamorphic events. This reconstruction gives new insights in the tectonic setting of metamorphic units below the Tuscan Nappe, in southern Tuscany. Particularly, the medium and high grade metamorphic rocks seem strictly related to the development of Neogene thermal aureoles and do not represent remnants of a Paleozoic basement. Furthermore, in this sector of the Larderello geothermal system, the presence of deep geothermal reservoir at a depth of 3 000 m is mainly linked to the enhanced permeability caused by fracturing in these hornfels rocks. This fracturing is a consequence of the dehydration reaction occurring in the metapelites due to Neogene thermal metamorphism. This mechanism allowed the development of a long-lived hydrothermal system, shown by the secondary mineralogical assemblages. These testify the presence of at least two hydrothermal stages which are well preserved in the less permeable units. © 2000 Editions scientifiques et médicales Elsevier SAS  相似文献   

造山过程重力塌陷与褶皱作用——面理弯切轴与褶皱轴面数据对比研究          下载免费PDF全文

曹汇 《中国地质》2013,40(6):1818-1828

提要：美国东部阿巴拉契亚造山带北端缅因州Rangeley地区志留—泥盆纪中温低压片岩测得的面理弯切轴与褶皱轴面数据有很好的对应关系。西部科迪勒拉造山带落基山脉南端科罗拉多州阿肯色河地区Texas Creek 以东高温低压前寒武纪堇青石片岩中测得的褶皱轴面方向和片理走向数据与该地区堇青石、斜长石变斑晶内测得的5期面理弯切轴也表现出很好的一致性。而在Rangeley北东200 km的佛蒙特州Chester Dome地区奥陶—泥盆纪中温中压片麻岩中测得的类似褶皱轴面数据却只反映了该地区5期面理弯切轴中较晚的北北西-南南东走向和北北东-南南西走向的两期面理弯切轴,未测得与其余3期面理弯切轴对应的褶皱轴面数据。通过对变质峰期温度相近、压力不同的两个造山带内3个典型变质岩区面理弯切轴、褶皱轴面方向和片理走向数据的对比分析认为,造山作用发生的地壳深度差异是早期褶皱经历多期造山运动后能否保存下来的主要影响因素。重力形成的去褶皱作用使得早期形成的规模较小褶皱经历复杂造山过程后难以保存。区域内早期形成的规模较大褶皱和造山过程晚期形成的褶皱由于受到重力塌陷作用影响较小,所以能够较好保存下来。  相似文献   

大别山及邻区若干重要基础地质问题的再认识:再论大别造山带非板块碰撞造山过程   总被引：1，自引：0，他引：1  

汤家富  侯明金 《地学前缘》2016,23(4):1-21

就大别山及邻区若干重要基础地质问题作了较深入阐述,并据前人资料与新近调查成果,进一步明确：(1)北淮阳地区属扬子地块北缘,与华北地块南缘的分界为固始-肥中断裂以北。(2)超高压变质带内新元古代浅变质岩层确系存在,并与榴辉岩及其他超高压岩石,共同经受两期褶皱变形,形成早期为伸展拆离,主期为收缩挤压叠加褶皱变形带,而非外来构造残片,或俯冲过程被铲刮下来的“构造加积楔”。(3)蓝片岩形成于伸展拆离构造带内。榴辉岩为地幔岩,属岩浆成因。其他超高压岩石与“柯石英”可在“地壳异常压力”与“高压釜”机制联合作用下,在地壳较浅层次的伸展拆离构造环境下形成。(4)广泛分布的新元古代火山岩系及侵入岩,代表了晋宁期地壳被强烈拉伸裂解扩张事件,但未形成洋壳盆地。(5)详细描述了大别山及邻区构造变形及拉伸与生长线理特征以及形成机制,认为是由“地幔差速环流”所引发的岩石圈与地壳各分层间伸展拆离滑断剪切过程中形成。大别造山带经历了裂解成盆、伸展拆离、收缩挤压、热隆成山,由多阶段构造运动所完成,而非板块碰撞造山。  相似文献