First finds of Permian conodonts in eastern Iran and once again on the Guadalupian series base in Permian sections of the Tethyan realm

Conodonts found for the first time in eastern Iran (the Bage-Vang section) are characterized. Beds with conodonts also yield fusulinids that is suitable for refining correlation of conodont and fusulinid zonations. Stratigraphic ranges of different conodont species in the Bage-Vang section are correlated with those in the Luodian section (South China), where conodonts are also accompanied by fusulinids. As a result, some previous inferences concerning position of the Guadalupian Series base in the Tethyan sections are refined.     

Plume head–lithosphere interactions near intra-continental plate boundaries

Plume–lithosphere interactions (PLI) have important consequences both for tectonic and mineralogical evolution of the lithosphere: for example, Archean metallogenic crises at the boundaries of the West African and Australian cratons coincide with postulated plume events. In continents, PLI are often located near boundaries between younger plates (e.g., orogenic) and older stable plates (e.g., cratons), which represent important geometrical, thermal and rheological barriers that interact with the emplacement of the plume head (e.g., Archean West Africa, East Africa, Pannonian–Carpathian system). The observable PLI signatures are conditioned by plume dynamics but also by lithosphere rheology and structure. We address the latter problem by considering a free-surface numerical model of PLI with two stratified elasto-viscous–plastic (EVP) lithospheric plates, one of which is older and thicker than another. The results show that: (1) plume head flattening is asymmetric, it is blocked from one side by the cold vertical boundary of the older plate, which leads to the mechanical decoupling of the crust from the mantle lithosphere, and to localized faulting at the cratonic margin; (2) the return flow from the plume head results in sub-vertical down-thrusting (delamination) of the lithosphere at the margin, producing sharp vertical cold boundary down to the 400 km depth; (3) plume head flattening and migration towards the younger plate results in concurrent surface extension above the centre of the plume and in compression (pushing), down-thrusting and magmatic events at the cratonic margin (down-thrusting is also produced at the opposite border of the younger plate); these processes may result in continental growth at the “craton side”; (4) topographic signatures of PLI show basin-scale uplifts and subsidences preferentially located at cratonic margins. Negative Rayleigh–Taylor instabilities in the lithosphere above the plume head provide a mechanism for crustal delamination. Inferred consequences of PLI near intra-continental plate boundaries, such as faulting at cratonic edges and enhanced magmatic activity, could explain plume-related metallogenic crises, as suggested for West Africa and Australia.     

郯庐断裂带的两大发展阶段——广义的逆冲推覆断裂带和狭义的平移断裂带

笔者总结了近年来的研究成果认为．中国东部的郯庐断裂带白海西期以来经历了两个主要发展阶段：第一阶段是广义的郯庐断裂带发展阶段，晚三叠世-早侏罗世由于扬子地块与华北地块的碰撞，成为两地块的对接边界，具有逆冲推覆的性质，属广义的特提斯构造域。第二发展阶段从早白垩世以来，发展成为一条平移断裂带，属于狭义的环太平洋构造域的平移系统。岩相古地理资料显示了扬子地块与华北地块的对接始于晚二叠世早期：印支期的郯庐断裂带是一条由NE、NNE向展布的缓‘S’型的地块拼贴边界．在现今的郯庐断裂带上表现为残留的由北北西向南南东的斜向逆冲推覆的性质，中下构造层次表现为韧性逆冲推覆变形，上部构造层即前陆褶皱冲断带内的变形：应力场分析资料显示：早三叠世晚期开始地表浅部就有近南北向的挤压作用，左行走滑平移作用开始发育：早白垩世晚期开始转入引张伸展阶段．与中国东部的伸展作用一致：新近纪又转为近东西向挤压．发育逆冲兼右行走滑作用．     

Multi-stage volcanic events: A statistical investigation

Volcanic events comprising multiple eruptive stages are common in the historical and geological record and display activity of variable intensity ranging, in some cases, through to several centuries. To better understand the characteristics of such events globally, this study explores a database of historical events having Volcanic Explosivity Indices 4 or greater. The database was compiled for the most part from published and unpublished material provided by the Smithsonian Institution. The database was examined to find common statistical relationships, within and between the variables characterising multi-stage explosive events.     

四川天宝山铅锌矿成矿物质来源与成矿机制：来自流体包裹体及同位素地球化学制约

天宝山铅锌矿床位于扬子地台西缘,为川滇黔铅锌矿集区具有代表性大型铅锌矿床,其金属储量(Pb+Zn)可达2.6Mt,铅锌品位10%～15%。本文在系统的分析流体包裹体和C、H、O、S、Pb、Sr同位素研究的基础上,确定其成矿物质来源、成矿流体性质及来源,并探讨其成矿机制。H-O同位素及流体包裹体研究表明,成矿流体具有中低温(均一温度峰值为140～200℃)及中低盐度(盐度峰值为6%～12% NaCleqv)的特征。灯影组白云岩与海相沉积碳酸盐岩的C、O同位素组成较为相似,热液方解石与含矿白云岩O同位素组成均稍低于灯影组白云岩,表明成矿流体中的CO_2可能来源于海相碳酸盐岩的溶解。矿区硫化物δ~(34)S值介于1.1‰～7.5‰之间,表明S主要来源于灯影组中硫酸盐热化学还原作用和岩浆硫的混合。矿石硫化物的Pb同位素比值在Pb演化图解上主要落入上地壳与造山带之间,表明Pb具有壳源特征,成矿物质来源主要来自于盖层沉积岩和基底地层。闪锌矿的~(87)Sr/~(86) Sr值(0.71099～0.71856)及热液方解石~(87)Sr/~(86) Sr值(0.71014～0.71169)均高于灯影组白云岩~(87)Sr/~(86) Sr值(0.70773～0.71026),表明成矿流体流经了具有高~(87)Sr/~(86) Sr值的基底地层,并与其发生水岩反应及同位素交换。     

东天山晚古生代-中生代构造演化和内生金属矿床成矿系列

本文立足于东天山地区晚古生代-中生代内生金属矿床的野外地质研究,在充分整理和消化前人大量研究成果的基础之上,选取典型矿床进行重点解剖研究,尝试应用成矿系列的理论来认识东天山晚古生代-中生代内生金属矿床的时空分布和成矿动力学演化规律,以内生金属矿床时空分布样式作为大地构造环境的标志和限定;本文主要以东天山地区的内生金属矿床为研究对象,并按照成矿系列的学术思想,将其进一步划分为5个成矿亚系列。按照时代顺序,对于每一个成矿系列形成的成矿动力学背景、时空分布规律、典型矿床特征和成因机制进行了简要论述;基于对成矿系列的分析研究,进而探讨了东天山晚古生代-中生代内生金属矿床规律与构造演化之间的关系;总结了该地区古生代俯冲-增生和中生代后碰撞演化导致了该地区独居特色的内生金属矿床侧向分带现象;指出东天山作为中亚增生造山带的重要组成部分,古生代-中生代的构造经历了完整的俯冲-增生、碰撞造山和后碰撞的演化阶段,而每一个构造演化阶段都伴随有一套内生金属矿床成矿系列和金属元素的大量堆积。     

洋中脊拆离断层与洋底核杂岩的发育对扩张中心迁移的影响研究

洋中脊拆离断层和洋底核杂岩（OCC）发育于慢速-超慢速扩张洋中脊中央裂谷边界,常伴随不对称的洋底扩张方式,其形成与演化起源于洋中脊中央裂谷间歇性的岩浆作用循环。拆离断层的规模和位置会随其自身演化而变化,并影响到洋中脊扩张中心的位置变化。依据洋中脊扩张中心位置的离轴迁移规律,本文将拆离断层和洋底核杂岩的演化过程划分为6个阶段,并参照洋中脊拆离断层和洋底核杂岩演化阶段的划分,将全球27处拆离断层进行分类。现今全球洋中脊拆离断层多属于非活动性拆离断层,位于阶段VI（如Logachev Massif拆离断层和Kane Megamullion拆离断层）;但部分拆离断层仍在活动,即属于发展期和成熟期（阶段III/IV,如MAR, 13°19′N拆离断层和MtDent拆离断层）,以及衰亡期（阶段V,如MAR, 13°30′N拆离断层和Atlantis Massif拆离断层）。在洋中脊拆离断层和洋底核杂岩形成-演化-衰亡-再次形成的循环过程中,中央裂谷的岩浆作用发生周期性循环,洋中脊扩张中心亦发生新生火山岩区中线-拆离断层终止线-重新活动的新生火山岩区中线的位置变化,并先后产生离轴和向轴的位移。     

内蒙古自治区水泉沟果园铁铜矿成矿特征分析

研究区位于内蒙古大兴安岭南段,属古亚洲成矿带与环太平洋成矿带复合叠加部位,通过矿产地质调查,发现该区内有Fe,Cu等多金属矿化现象,通过对研究区岩石特征、物化探异常、矿体特征等分析,确定该地区为岩浆热液型铁铜矿床,有良好的成矿前景,为该区进一步寻找隐伏矿床提供依据。     

小秦岭东桐峪金矿床的流体包裹体研究

东桐峪金矿床位于小秦岭金矿田的中西部,其含金石英脉受韧性剪切构造带的控制。该矿床的构造-成矿过程可划分为4个阶段:Ⅰ黄铁矿-乳白色石英脉阶段;Ⅱ灰白色石英-黄铁矿阶段;Ⅲ石英-多金属硫化物阶段;Ⅳ石英-碳酸盐阶段。相对于小秦岭地区的其他金矿床,东桐峪金矿床的流体包裹体研究资料相对缺乏。文章表明,该矿床内的流体包裹体类型主要为CO₂-H₂O包裹体和水溶液包裹体,见少量纯液相CO₂包裹体。显微测温表明,Ⅰ阶段的构造-成矿流体以中温、富CO₂等挥发分为特征,包裹体均一温度为221~392℃,盐度w(NaCl_eq)为5.5%~7.9%,密度为0.84~0.93 g/cm³;Ⅱ阶段和Ⅲ阶段以CO₂-H₂O±CH₄流体为主,包裹体均一温度为205~350℃(Ⅱ阶段)和224~271℃(Ⅲ阶段),盐度w(NaCl_eq)集中于5.1%~7.1%,密度为0.83~0.96 g/cm³;Ⅳ阶段的流体演化为中-低温、低盐度的盐水溶液体系,包裹体均一温度为175~185℃。文章对该矿床各成矿阶段的压力进行了估算,Ⅰ、Ⅱ、Ⅲ阶段的流体最小捕获压力分别为123~160 MPa、160~170 MPa、170 MPa左右。