北太行山安妥岭斑岩钼矿Pb同位素组成及地质意义     

卢仁  梁涛  罗照华  樊秉鸿 《矿产与地质》2013,(1):83-88

对安妥岭斑岩钼矿床矿石中辉钼矿和黄铁矿进行了Pb同位素分析。安妥岭黄铁矿样品投点位于下地壳铅演化趋势线附近,辉钼矿样品投点位于上地幔铅演化趋势线附近;在Pb同位素Δβ-Δγ图解中,安妥岭样品数据点位于地幔源区和造山作用源区。这些Pb同位素特征表明安妥岭斑岩钼矿的成矿物质来源于上地幔-下地壳。同时,安妥岭斑岩钼Pb同位素示踪揭示了成矿期的构造运动波及到上地幔-下地壳,与安妥岭岩石圈拆沉作用这一深部动力学过程相吻合,安妥岭斑岩钼矿受控于太行山板内造山过程,其形成与太平洋板块的俯冲作用无关。  相似文献   

云南马关碧(钾)玄质火山角砾岩中矿物混晶包体特征及其地质意义          下载免费PDF全文

黄玉蓬  刘显凡  李春辉  卢秋霞  陶专  赵甫峰  董毅  邹金汐  易立文 《地学前缘》2013,20(2)

在云南马关碧(钾)玄质火山角砾岩中发现了一类特殊包体,呈红色与黑色两种。经X射线粉晶衍射鉴定,红色者为以锰铝榴石为主要结晶相的隐晶—非晶质混晶,黑色者为以绿辉石为主要结晶相的隐晶—非晶质混晶。两种矿物混晶包体在一定程度上类似于熔浆玻璃或熔体囊,它们具有同源演化的相似地球化学特征。文中通过对两种矿物混晶包体的显微特征与地球化学分析研究表明,它们是亏损地幔部分熔融的产物,并作为一种不混溶熔体成分被碱性玄武岩浆携带、运移上升。它们代表了石榴石相(榴辉岩相)地幔源区组分,暗示新生代时期软流圈上涌除释放小体积交代熔体交代上地幔使其富集之外,还造成岩石圈地幔拆沉,尖晶石相地幔组分向石榴石相地幔组分转变。另外,据两种混晶包体与其他类型包体和寄主岩岩浆的不同来源,推测马关地区深部岩石圈地幔经交代作用发生过两次转换。首先是由原始地幔向亏损地幔转化,并发生部分熔融,其后是由亏损地幔转化为富集地幔,形成富碱岩浆和与其互不混溶的进一步富集成矿元素的地幔流体。由此暗示滇西地区与富碱斑岩有关的多金属成矿作用即受制于这一深部地质过程与壳幔混染机制。  相似文献   

豫西崤山后河岩体LA-ICP-MS锆石U-Pb定年   总被引：9，自引：0，他引：9  

卢仁  梁涛  卢欣祥  白凤军 《前寒武纪研究进展》2013,(4):263-270

与豫西小秦岭和熊耳山地区相类似,崤山北部也出露一系列中酸性小岩体,但与之相关的成矿作用明显较弱,因此长期未获得应有的关注。崤山北部小岩体的形成时代与区域成岩成矿时代之间的匹配关系对其深部构造演化研究及成矿潜力评价具有重要意义,鉴于此,作者对后河岩体进行了LA—ICP—MS锆石U-Db定年。后河岩体定年样品HH01的岩性为中一细粒黑云母二长花岗岩,30个锆石测点中有27个测点的测定值位于207PB/235U-206Pb/238U一致线上,相应的206Pb/238U年龄介于124～134Ma之间,加权平均年龄为128±1Ma（MSWD=I．02）,属早白垩世。后河岩体是岩石圈拆沉作用的产物,其形成时代处在东秦岭地区广泛而强烈的成岩成矿作用时限内,且显示了Au、Ag、Cu、Mo、W等元素的异常富集,具有较大的内生金属成矿潜力。  相似文献   

豫西磨沟正长岩LA-ICP-MS锆石U-Pb年代学及Hf同位素   总被引：4，自引：0，他引：4  

卢仁  梁涛  白凤军  卢欣祥 《地质论评》2013,59(2):355-368

河南省东秦岭地区印支期岩浆活动产物零星出露,豫西外方山纸房—黄庄地区是其产地之一,本文对纸房—黄庄地区出露面积最大的磨沟正长岩岩体进行了LA-ICP-MS锆石U-Pb定年及Hf同位素测试.磨沟正长岩的锆石206 Pb/238U谐和年龄为245.5 ±8.0Ma(95%置信度,MSWD=2.6),记录了秦岭造山带印支期内早三叠世碱性岩浆活动事件.磨沟正长岩样品的εHf(t)值介于-31.89～-10.59之间,聚集于-31.89～-27.64和-21.02～-10.59两个区间内,二阶段Hf模式年龄(tDM2)为1937～3267Ma,集中于1937～ 2591 Ma和3003 ～ 3267 Ma两个年龄范围内.锆石Hf同位素特征表明磨沟正长岩是幔源碱性岩浆与壳源花岗质岩浆(片麻岩部分熔融)相混合的产物,与磨沟正长岩岩体中出现暗色微粒包体这一地质特征相吻合.磨沟正长岩形成于秦岭造山带的面接触碰撞时期,长期持续的碰撞效应使纸房—黄庄岩石圈厚度在垂向上显著增厚,其重力不稳定性加强,在印支早期发生局部小规模拆沉,与之伴有大规模的深部流体活动,暗示纸房—黄庄地区具有巨大成矿潜力,尤其是与正长岩岩体自身相关的稀有(Rb、Zr)、轻稀土元素及非水溶性钾矿资源.  相似文献   

An Overview of the Destruction of North China Craton     

YANG Xiaonan  LI Zhonghai 《《地质学报》英文版》2013,87(Z1):177-178

  相似文献   

大别山东缘郯庐两期走滑剪切带形成的温压条件与造山带折返的关系   总被引：16，自引：8，他引：8  

王勇生  朱光  王道轩  刘国生  宋传中 《大地构造与成矿学》2004,28(3):228-238

郯庐断裂带与大别造山带在大别山东缘相复合 ,并将大别—苏鲁造山带左行错开达 5 0 0km。本文以大别山东缘为研究背景 ,通过对郯庐断裂带两期左旋走滑韧性剪切带温压条件的估算及热年代学信息的分析 ,来探讨大别造山带在早侏罗—早白垩世之间的折返历史与隆升量。通过矿物组合、矿物变形特征以及白云母—绿泥石地质温度计得到郯庐早、晚两期剪切带的形成温度均为 4 0 0～ 4 5 0℃。通过多硅白云母Si原子数地质压力计计算得到早、晚两期剪切带的形成压力分别为 0 .2 5～ 0 .36GPa和 0 .2 4～ 0 .39GPa。考虑到剪切摩擦加热和构造超压的影响 ,笔者推断郯庐两期走滑剪切带形成的最大深度均不超过 12km ,且两期走滑剪切带的形成深度至多相差 1～2km。郯庐断裂带在约 190Ma和 12 8Ma经历了两期走滑冷却事件 ,而在此期间 ,大别造山带东缘经历了一个构造平静期 ,基本没有发生隆升。根据郯庐断裂带的信息 ,造山带在早白垩世的热隆事件中的隆升幅度小于 12km。  相似文献   

长江中下游成矿带岩石圈结构与成矿动力学模型——深部探测(SinoProbe)综述   总被引：23，自引：10，他引：13  

吕庆田  董树文  史大年  汤井田  江国明  张永谦  徐涛  SinoProbe--CJ项目组 《岩石学报》2014,30(4):889-906

岩石圈结构和深部过程对理解成矿带和大型矿集区的形成十分重要。岩石圈尺度的地球动力学过程将在地壳中留下各种结构的或物质的"痕迹",这些"痕迹"可以通过地球物理的手段去探测。为深入理解长江中下游成矿带形成的深部动力学过程,作者在国家深部探测专项(SinoProbe)和国家自然科学基金重点项目支持下,在长江中下游成矿带开展了综合地球物理探测。方法包括宽频地震、深地震反射、广角反射/折射和大地电磁测深。数据处理和反演结果取得一系列新发现:(1)成矿带上地幔顶部存在低速体,在中心深度300km处有一向SW倾斜的高速体;(2)S波接收函数证实成矿带岩石圈较薄,只有50~70km;横波分裂结果显示,成矿带上地幔各向异性方向和强度与邻区有较大区别,显示平行成矿带(NE-SW向)的上地幔变形和流动;(3)深反射地震揭示成矿带上地壳曾发生强烈挤压变形,以紧闭褶皱、逆冲和推覆为特征;在宁芜火山岩盆地、长江断裂带和郯庐断裂之下出现"鳄鱼嘴"构造,指示上下地壳在挤压变形过程中解耦;深反射地震证实发生过陆内俯冲和叠瓦,并认为是岩石圈增厚和拆沉的主导机制;(4)广角反射和大地电磁反演给出了跨成矿带地壳剖面的速度和电性结构,速度和电阻率分布总体上与构造单元相吻合。本文分析和解释了这些发现的地质意义,并结合近年在长江中下游地区的地球化学研究进展,提出了成矿带地球动力学模型。该模型认为:中、晚侏罗世陆内俯冲、岩石圈拆沉、幔源岩浆底侵和MASH过程造就了长江中下游世界级成矿带的形成。  相似文献   

Delamination of smectite in river-borne suspensions at the fluvial/marine interface – An experimental study     

Olaf Brockamp 《Estuarine, Coastal and Shelf Science》2011

Fine fractions (<2 μm) from smectite-rich flood-plain sediments from the Elbe and Weser rivers in Germany were treated in the laboratory with synthetic sea salt solutions at different concentrations and for different periods of time to document sheet delamination of smectite particles at the fluvial/marine interface and thus simulate changes in clay minerals at the mouth of a river. The project consisted of two steps: (1) Pilot tests were made in 0.5% salt solutions (brackish environment) showing a nearly 2-min delay of the clearing of the clayey suspensions, when the suspension was redispersed 15 and 30 min later after the first measurement. This was due to an obviously increased number of fine laminae from disintegrated smectite particles. (2) X-ray diffraction studies (XRD) of the clayey material from suspensions in 0.0, 0.5, 1.0, and 3.0% salt solutions after standing 10 min, and one and three weeks were made to document alteration reactions of smectite. An aliquot was pipetted periodically from each series, and oriented clay-mineral specimens were analyzed by XRD in air-dried, glycol- and glycerin-solvated states. The peak intensities in the XRD patterns of the clay minerals smectite, random-ordered mixed-layer illite/smectite (I–S), kaolinite, chlorite, and illite did not change in the salt-free series during the experiments. In contrast the peak intensities of smectite and I–S mineral in the air-dried and glycerin-solvated states after suspension in saline solutions decreased significantly. The d-values of the smectitic materials in the air-dried state also decreased after contact with the saline solutions, and in the glycerin-solvated state the full-width-at-half-maximum (FWHM) of the 001 smectite reflection increased by about 20%, indicating a reduction in grain size.  相似文献   

Petrogenesis and metallogenic implications for the Machang,Huangdaoshan, and Tuncang plutons in eastern Anhui: an integrated age,petrologic, and geochemical study     

Yu Fan  Xuefeng Chen  Yinan Liu  Wei Zhang  Taofa Zhou 《International Geology Review》2018,60(11-14):1581-1593

ABSTRACT

The Tuncang–Chuzhou–Machang area (eastern Anhui province) is geologically located in the intersection between the Yangtze block and the Qinling–Dabie orogenic belt. Many Mesozoic plutons outcrop in this district that are Cu–Au prospective but inadequately studied. We report new LA-ICP-MS zircon U–Pb ages, petrologic, and whole rock geochemical data for three representative plutons at Machang, Huangdaoshan, and Tuncang. New dating results suggest that all the Machang (129.3 ± 1.6 Ma), Huangdaoshan (129 ± 1.7 Ma), and Tuncang (130.8 ± 1.9 Ma) plutons were emplaced in the Early Cretaceous, slightly older than other plutons in neighbourhood of the Zhangbaling uplift. The three plutons contain typical low-Mg adakitic affinities, in which the rocks contain SiO₂ >56%, Al₂O₃ ≥15%, Mg# <53, elevated Sr, Ba, Cr, Ni, Sr/Y, and La/Yb, low Y and Yb and no discernible Eu anomaly. Their petrogenesis may have been related to the delamination and partial melting of the lower crust, which is different from the Chuzhou pluton, which was interpreted to have formed by partial melting of the subducted slabs. We suggest that this petrogenetic difference may explain why the pluton at Chuzhou is Cu–Au fertile, whereas those at Machang, Huangdaoshan, and Tuncang are largely barren. It is proposed that adakitic plutons formed by partial melting of the subducted slabs have high metallogenetic potentiality in the area.  相似文献   

Origin of Early Cretaceous Guandian adakitic pluton in central eastern China: partial melting of delaminated lower continental crust triggered by ridge subduction     

Ze-Bin Luo  Shuo Xue  Li-Peng Zhang  He Li  Cong-Ying Li  Hong Zhang 《International Geology Review》2018,60(11-14):1707-1720

ABSTRACT

Early Cretaceous adakite or adakitic plutons are widely distributed in central eastern China, e.g. lower Yangtze river belt (LYRB), the south Tan–Lu fault (STLF), and the Dabie orogen. Their genesis, however, remains controversial. In this contribution, we present detailed geochemical and geochronological study on the Guandian pluton in central Anhui Province, eastern China, which has been formerly regarded as a part of the north belt in the LYRB and lately classified in the STLF. Namely, it is located near the boundary between ridge subduction related slab melting and partial melting of lower continental crust (LCC). The Guandian pluton consists of quartz monzonite and is metaluminous and high-K calc-alkaline according to the chemical composition. The samples show high SiO₂ (59.15–62.32%), Al₂O₃ (14.51–15.39%), Sr (892–1184 ppm), Sr/Y (56.74–86.32), and low Y (12.65–18.05 ppm), similar to typical geochemical features of adakite. The Guandian adakitic rocks also exhibit high K₂O (2.88–3.86%), MgO (3.89–5.24%), and Mg# (55–60), negative anomalies of high field strength elements (e.g. Nb, Ta, and Ti), and positive anomalies of Ba, Pb, and Sr. LA-ICP-MS zircon U–Pb dating yielded a weighted average age of 129.2 ± 0.7 Ma. Calculations of zircon Ce⁴⁺/Ce³⁺ (6.97–145) and (Eu/Eu*)_N (0.23–0.42) on the basis of in situ zircon trace element analysis indicate that the magma had a lower oxygen fugacity relative to the ore-bearing adakites in the LYRB and Dexing, which is consistent with the fact of ore-barren in the research area. In combination with previous research, we propose that Guandian adakitic pluton was formed by partial melting of delaminated LCC triggered by Early Cretaceous ridge subduction of the Pacific and Izanagi plates. During ridge subduction, physical erosion destructed the thickened LCC and resulted in delamination, while thermal erosion facilitated partial melting of the delaminated LCC.  相似文献