江西银山矿区次火山岩岩石地球化学特征及形成大地构造环境   总被引：11，自引：1，他引：10  

乐小横  徐旭荣  郝青振 《大地构造与成矿学》2000,24(4):385-389

银山矿区次火山岩主要可分为三类 ,1石英斑岩 2英安斑岩 3安山玢岩 ,它们均属于一套高钾钙碱性的中酸性花岗岩系列。矿区次火山岩中 ,Cu、Ag、Pb、Zn等成矿元素均高出同类岩性克拉克值 1倍以上 ,表明次火山岩与矿床形成关系密切。岩石地球化学特征表明 :矿区次火山岩属幔壳混合源 ,它们分别形成于幔源花岗岩区 ,板块碰撞前消减区 (消减的活动板块边缘 )和板块碰撞后隆起花岗岩区 ,这说明与矿床有关的火山活动发生在成熟的陆壳构造之上受太平洋板块向陆壳板块俯冲影响而形成的活动大陆边缘。成矿时代为燕山早期晚阶段  相似文献   

长坑金矿床地质特征与成因探讨   总被引：4，自引：0，他引：4  

关康  裘有守  颜竹筠 《地质与资源》1997,6(1):27-37

通过含矿复成因角砾岩带特征,金矿物,微量元素,稀土,硫、氢、氧稳定同位素和流体包裹体研究,确定成矿物质主要来自下石炭统碳酸盐岩,滑脱断裂叠加不整合面为控矿构造,矿体主要赋存在复成因角砾岩带中,成矿流体以大气水为主,矿床成因属浅成低温热液矿床.  相似文献   

Nature and origin of cone-forming volcanic breccias in the Te Herenga Formation, Ruapehu, New Zealand   总被引：1，自引：1，他引：0  

Gary A. Smith  Michael J. Grubensky  John W. Geissman 《Bulletin of Volcanology》1999,61(1-2):64-82

 Volcanic breccias form large parts of composite volcanoes and are commonly viewed as containing pyroclastic fragments emplaced by pyroclastic processes or redistributed as laharic deposits. Field study of cone-forming breccias of the andesitic middle Pleistocene Te Herenga Formation on Ruapehu volcano, New Zealand, was complemented by paleomagnetic laboratory investigation permitting estimation of emplacement temperatures of constituent breccia clasts. The observations and data collected suggest that most breccias are autoclastic deposits. Five breccia types and subordinate, coherent lava-flow cores constitute nine, unconformity-bounded constructional units. Two types of breccia are gradational with lava-flow cores. Red breccias gradational with irregularly shaped lava-flow cores were emplaced at temperatures in excess of 580  °C and are interpreted as aa flow breccias. Clasts in gray breccia gradational with tabular lava-flow cores, and in some places forming down-slope-dipping avalanche bedding beneath flows, were emplaced at varying temperatures between 200 and 550  °C and are interpreted as forming part of block lava flows. Three textural types of breccia are found in less intimate association with lava-flow cores. Matrix-poor, well-sorted breccia can be traced upslope to lava-flow cores encased in autoclastic breccia. Unsorted boulder breccia comprises constructional units lacking significant exposed lava-flow cores. Clasts in both of these breccia types have paleomagnetic properties generally similar to those of the gray breccias gradational with lava-flow cores; they indicate reorientation after acquisition of some, or all, magnetization and ultimate emplacement over a range of temperatures between 100 and 550  °C. These breccias are interpreted as autoclastic breccias associated with block lava flows. Matrix-poor, well-sorted breccia formed by disintegration of lava flows on steep slopes and unsorted boulder breccia is interpreted to represent channel-floor and levee breccias for block lava flows that continued down slope. Less common, matrix-rich, stratified tuff breccias consisting of angular blocks, minor scoria, and a conspicuously well-sorted ash matrix were generally emplaced at ambient temperature, although some deposits contain clasts possibly emplaced at temperatures as high as 525  °C. These breccias are interpreted as debris-flow and sheetwash deposits with a dominant pyroclastic matrix and containing clasts likely of mixed autoclastic and pyroclastic origin. Pyroclastic deposits have limited preservation potential on the steep, proximal slopes of composite volcanoes. Likewise, these steep slopes are more likely sites of erosion and transport by channeled or unconfined runoff rather than depositional sites for reworked volcaniclastic debris. Autoclastic breccias need not be intimately associated with coherent lava flows in single outcrops, and fine matrix can be of autoclastic rather than pyroclastic origin. In these cases, and likely many other cases, the alternation of coherent lava flows and fragmental deposits defining composite volcanoes is better described as interlayered lava-flow cores and cogenetic autoclastic breccias, rather than as interlayered lava flows and pyroclastic beds. Reworked deposits are probably insignificant components of most proximal cone-forming sequences. Received: 1 October 1998 / Accepted: 28 December 1998  相似文献   

安徽省境内宿松群与大别群接触关系性质的厘定     

侯明金  汤加富  高天山  荆延仁 《现代地质》1998,12(4):541

摘 要　 运用构造地层学的理论和方法‚详细解剖了安徽省境内宿松群与大别群在几个重要地 段（猪婆寨、梓树坞、杨岩、大新屋和柳坪）接触关系的性质‚提出宿松群南西部的大别群主 要是变形变质侵入体‚与宿松群为先侵入、后构造的接触关系。在宿松群大新屋组厚层白云 质大理岩之上发现多层透镜状层间砂砾岩层‚沉积和构造标志均显示其层位在大新屋组之上 （新建为梓树坞组）‚对原来认为的不整合接触关系和底砾岩提出质疑。  相似文献   

安徽枞阳县黄龙桥地区隐爆角砾岩筒特征及其与铀成矿关系     

杨彪 《地质与勘探》2024,60(3):471-481

安徽枞阳黄龙桥地区隐爆角砾岩筒地处庐枞盆地黄梅尖A型花岗岩体内,是岩体内发育的规模最大、最为典型的隐爆角砾岩筒。文章在详细的野外地质调查、物化探测量和钻孔岩心地质编录的基础上,通过显微岩石学、元素地球化学特征研究,分析其地质特征并探讨其与铀成矿的关系。分析研究表明：隐爆角砾岩具有角砾成分杂、隐爆作用强度大、“隐爆源”埋藏深特点,其自身并不含有铀矿化现象,铀元素平均含量远远低于石英正长岩;ΣREE为293.16×10-6~453.45×10-6,LREE/HREE为6.71~11.00,δCe为0.89~1.02,δEu为0.46~0.57,呈现较明显的负Eu异常,稀土元素配分模式呈右倾斜型,具有轻稀土分馏明显,重稀土分馏不明显的特点;隐爆角砾岩内部发育的大量赤铁矿形成于岩浆“隐爆”作用之前,铀成矿作用发生在隐爆角砾岩筒形成之后,推测隐爆角砾岩爆发时间在124~115 Ma;隐爆角砾岩筒主要为铀成矿提供了重要的导矿通道,外围具有较好的铀矿找矿潜力,而其深部具有寻找铁矿的潜力。  相似文献   

西藏斯弄多银多金属矿床热液角砾岩特征及成因分析     

郝金月  冉凤琴  多吉  唐菊兴  杨宗耀  吴鑫  杨昕  宋壮壮 《矿床地质》2021,40(3):509-522

西藏斯弄多银多金属矿床产于陆相林子宗群火山岩内,是冈底斯成矿带发现的首例浅成低温热液矿床.矿床具有热液脉型银铅锌矿体、隐爆角砾岩型矿体和独立银矿体"三位一体"的矿体组合形式.热液角砾岩作为矿区主要矿(化)体,目前尚未开展详细研究工作.文章以斯弄多矿区热液角砾岩为研究对象,通过钻孔岩芯编录和岩相学研究,总结了不同类型热液...  相似文献