论砾岩层控型半宽金矿的地质特征和成因   总被引：1，自引：0，他引：1  

陈衍景  富士谷 《铀矿地质》1995,11(6):334-343

半宽金矿产于崤山地体铁铜沟组与下代岩层的不整合面或铁铜沟组底砾岩中，赋矿层金丰度明显高于其它岩石，属典型的层控矿床，称之砾岩层控型。矿物包裹体、同位素、微量元素等研究表明，矿床形成经历了Ⅰ期高温变质热液蚀变矿化、Ⅱ期中温变质－雨水混合热液蚀变矿化、Ⅲ期低温雨水热液蚀变矿化。Ⅲ期对矿床形成的贡献较小。成矿物质来源复杂，以深源为主。矿床形成于中生代沿马超营断裂向北的陆内俯冲作用，结晶基底与上覆地层的不整合面及上覆地层的底部是寻找半宽式金矿的有利位置。  相似文献   

桐柏-大别地区中温热液金矿床成矿流体性质与沉淀机理   总被引：14，自引：0，他引：14  

徐启东  钟增球  索书田  齐先茂 《矿床地质》1995,14(1):59-72

通过对桐柏－大别地区１０个中温热液金矿床（点）的流体包裹体研究，确定成矿流体属于低盐度（６ｗｔ％ＮａＣｌ），富ＣＯ２（１０ｍｏｌ％）的ＮａＣｌ－ＣＯ２－Ｈ２Ｏ体系。这种以演化的大气降水为主的流体在４～１０ｋｍ深度范围内，由于压力由静岩压力状态的向静水压力状态的空而发生的复杂三阶段不混溶过程中沉淀，在该过程的中晚期出现金矿化。压力状态的突变是柏桐－大别造山带在中生代碰撞造山晚期，由挤压体制向伸展体制  相似文献   

大别山地区三个花岗岩体的地球化学特征及其成因学意义   总被引：6，自引：0，他引：6       下载免费PDF全文

周承福  华仁民  马东升  陆建军  高剑峰 《地质找矿论丛》2001,16(2):81-88

大别山地区的主薄原，天柱山，白马尖三个花岗岩体主要由花岗闪长岩和二长花岗岩组成，岩石为准铝质到弱过铝质（ACNK＝0．78－1．05），为轻稀土富集型，富含大离子亲石元素Rb,Th，以及稀土元素La,Ce,Nd,Sm，通过花岗岩地质学，岩石学和地球化学研究，认为这在个岩体的地球化学特征相似，属I型花岗岩，其构造背景为碰撞后环境。  相似文献   

构造事件的沉积响应——建立青藏高原大陆碰撞、隆升过程时空坐标的设想和方法   总被引：10，自引：0，他引：10       下载免费PDF全文

伊海生  王成善  李亚林  林金辉  侯明才 《沉积与特提斯地质》2001,21(2):1-15

沉积盆地的地层形态、岩相类型以及空间配置样式是构造事件的重要标识，沉积序列中特征岩石组分的出现标志着毗邻造山带隆升的初始启动时间，与物源区地层单元垂向叠置序列相反或相同的岩屑组分剖面分布则是幕式构造旋回的反映，在前陆盆地中砾石层的出现被认为是冲断岩席活动的记录，而在断陷盆地和走滑拉分盆地中通常可识别出100m级的向上变粗和向上变细的旋回层，它们被解释为构造高地重复姓升和溯源侵蚀的结果，最近的研究工作表明，急剧的构造沉降主要是通过细粒级河湖相沉积补偿的，广泛的砾岩进积发生在构造活动的平静期，构造驱动的山脉隆升表现为砾岩地层呈楔状体，纵向河流水系发育；重力均衡回返所导致的山系隆升则形成以横向河流水系为主的板状砾岩沉积，从青藏高原腹地、周缘和外延海洋盆地的沉积记录中可获得取重大构造变革时期的信息，也许是解决目前有关印度与亚洲大陆碰撞、高原隆升等时性或穿时性以及限定陆内变形调节机制的一个重要手段。  相似文献   

The late Neoproterozoic Enganepe ophiolite, Polar Urals, Russia: An extension of the Cadomian arc?     

J. H. Scarrow  V. Pease  C. Fleutelot  V. Dushin 《Precambrian Research》2001,110(1-4)

The Enganepe ophiolite, Polar Urals was formed at 670 Ma and records a diverse geochemical association of tholeiite, arc-tholeiite, adakite, and OIB-like lithologies. This constrains the tectonic setting of the protolith of the ophiolite to an oceanic island-arc, with ridge-trench interaction most readily explaining the diverse compositions. The initiation of intra-ocean subduction and the development of the Enganepe island arc off the eastern margin of Baltica probably pre-dated the formation of the Enganepe ophiolite, i.e. prior to 670 Ma. The timing of island-arc magmatism is similar in age to that recorded off Avalon in the Cadomian arc. We propose that the active margin of Baltica in the Vendian is an extension of the Cadomian arc. This requires the northeast margin of Baltica (present-day coordinates) to have been in a southerly position in the Vendian, in agreement with proposed tectonic reconstructions. Consequently, the post-Rodinia continental amalgamation, Pannotia, had active ocean-continent convergence along its entire southerly (west Avalonia and Amazonian cratons) margin at the time of its break-up.  相似文献   

The geodynamic evolution of the Internal Zone of the Betic Cordilleras (south-east Spain): a model based on structural analysis and geothermobarometry   总被引：2，自引：0，他引：2  

H. E. BAKKER  K. DE JONG  H. HELMERS  C. BIERMANN 《Journal of Metamorphic Geology》1989,7(3):359-381

ABSTRACT The Internal Zone of the Betic Cordilleras consists of several superimposed major thrust sheets with different P-T-t evolutions. On the basis of an integrated field, microscopic and laboratory study, the tectono-metamorphic history of the Mulhacen Complex and Almanzora Unit has been reconstructed in detail. The Mulhacen Complex has been affected by at least five phases of penetrative deformation, which have been labelled D_x-1, D_x, D_x+1, D_x+2 and D_x+3. D_x-1, and D_x are related to continent-continent collision, which is indicated by high pressure-low temperature (HP/LT) and subsequent intermediate P/T metamorphic conditions. D_x+1 is related to crustal thinning and heterogeneous extension. During this event the Almanzora Unit was juxtaposed against the Mulhacen Complex. This phase was succeeded by the establishment of low pressure-high temperature (LP/HT) conditions and at least two phases of folding and overthrusting. The Almanzora Unit shows a comparable tectono-metamorphic evolution post D_x+1. However, the P/T conditions prior to D_x+1 indicate a higher crustal position with respect to the Mulhacen Complex during the collisional event.  相似文献   

辽宁北部早古生代弧－陆碰撞作用的发现及其构造意义     

时溢  石绍山  舒广龙 《地质与资源》1992,29(4):397-400

  相似文献   

Oblique subduction, collision of microcontinents and subduction of oceanic ridge: Their implications on the Cretaceous tectonics of Japan   总被引：2，自引：1，他引：2  

Kenshiro  Otsuki 《Island Arc》1992,1(1):51-63

Abstract The Izanagi plate subducted rapidly and obliquely under the accretionary terrane of Japan in the Cretaceous before 85 Ma. A chain of microcontinents collided with it at about 140 Ma. In southwest Japan the major part of it subducted thereafter, but in northeast Japan it accreted and the trench jumped oceanward, resulting in a curved volcanic front. The oblique subduction and the underplated microcon-tinent caused uplifting of high-pressure (high-P) metamorphic rocks and large scale crustal shortening in southwest Japan. The oblique subduction caused left-lateral faulting and ductile shearing in northeast Japan. The arc sliver crossed over the high-temperature (high-T) zone of arc magmatism, resulting in a wide high-T metamorphosed belt. At about 85 Ma, the subduction mode changed from oblique to normal and the tectonic mode changed drastically. Just after this the Kula/Pacific ridge subducted and the subduction rate of the Pacific plate decreased gradually, causing the intrusion of huge amounts of granite magma and the eruption of acidic volcanics from large cauldrons. The oblique subduction of the Pacific plate resumed at 53 Ma and the left-lateral faults were reactivated.  相似文献   

降水对气溶胶粒子清除的参数化   总被引：17，自引：1，他引：17  

彭红  秦瑜 《大气科学》1992,16(5):622-630

本文主要讨论了碰并系数、雨滴谱和气溶胶谱对湿清除率的影响.在0.1μm相似文献   

Anomalous granulite crust of South India — signatures from converted teleseismic waves     

D S Ramesh  D Srinagesh  S S RAI  K S PRAKASAM 《Journal of Earth System Science》1992,101(3):283-298

Analysis of teleseismic waves usingS-P converted phases, travel time-terms and residual travel times point to the presence of an anomalous thick (4—5 km thicker) low velocity (−3%) crust beneath Kodaikanal (KOD) on granulites characterized by an oriented inhomogeneity inferred as possibly due to Mylonites in contrast to the nature of crust beneath the adjoining precambrian granite-gneiss terrain. The observed seismic signatures in the South India granulites (represented by KOD) offer an opportunity to discriminate between the competing hypotheses of tectonic thickening and magmatic underplating to explain the origin of the granulites of South India. This analysis lends support to the hypothesis of a continent-continent collision origin for the granulites in the study region.  相似文献