安徽宣城薛家村隐爆角砾岩的发现及其找矿意义     

洪大军  陈科夫  张旭  金敏 《华东地质》2019,(4):280-288

宣城茶亭铜金矿床是首次在皖东南地区发现的大型斑岩型铜金矿床,成矿岩体上部发育大规模与成矿有关的隐爆角砾岩。近期,在茶亭矿区西侧薛家村南部也发现了隐爆角砾岩,通过野外地质调查、室内综合分析及地球物理特征对比,证明角砾岩成分、矿化蚀变及矿物组合特征与茶亭铜金矿床的隐爆角砾岩类似;薛家村一带的CSAMT低阻、激电高极化、中等地磁、重力高特征也与茶亭矿区相似。茶亭矿区西部被三叠系覆盖,薛家村隐爆角砾岩的发现,指示茶亭矿区可能存在多次隐爆作用,对茶亭铜金矿床外围进一步找矿具有指导意义。  相似文献   

Predicting the uniaxial compressive strength and elastic modulus of a fault breccia from texture coefficient   总被引：1，自引：0，他引：1  

M. Alber  S. Kahraman 《Rock Mechanics and Rock Engineering》2009,42(1):117-127

  相似文献   

Sedimentology, petrography and geochemistry of a limestone breccia (Pietra di Billiemi) from north-west Sicily, Italy: implications for evolution of the Tethyan basins around the Triassic/Jurassic boundary     

GIOVANNA SCOPELLITI  RODOLFO NERI  ADRIANA BELLANCA  PIETRO DI STEFANO†  MARIO BARBIERI‡ 《Sedimentology》2009,56(2):591-607

In this study, the Pietra di Billiemi , a famous dimension stone, is investigated because it records the tectonic evolution of the south Tethys continental margin and preserves a record of major environmental changes occurring near the Triassic/Jurassic boundary. The Pietra di Billiemi is a grey, coarse-grained and clast-supported limestone breccia cropping out in an area of the Palermo Mountains representing a segment of the Apennine–Maghrebian chain in western Sicily. The rock consists of metre-sized to centimetre-sized angular clasts, derived from Upper Triassic sponge boundstones and rudstones, with a differently coloured, silt-grained matrix. Fitted fragments are observed commonly which suggest an in situ origin for the bulk of the breccia. The matrix is characterized by the absence of biogenic components and by variable mineralogy and geochemistry. Petrographic features and Sr-isotope values indicate that the most important and earliest fillings of the breccia consist of black matrix and white matrix temporally referable to Hettangian–Sinemurian times. Clotted micrite, carbonate fluorapatite and abundant pyrite, in addition to relatively high contents of redox-sensitive elements (V, Ni, Zn and S), are consistent with deposition in anoxic conditions that favoured microbial mediation for authigenic carbonate (calcite and dolomite) precipitation in the matrix. As a whole, the Billiemi breccia can be considered a product of tectonic fragmentation of a Tethyan carbonate platform edge around the Triassic/Jurassic boundary, formed when the drowned platform edge was covered by hemipelagic mudstones recording the anoxic conditions existing during Early Jurassic times.  相似文献   

切特木斯铜（银）矿地质特征研究——兼论伊斯基里克地区“鸡窝”状矿体成因     

肖力  李汉光  董刚  金宝义  唐明国  韩先菊 《矿产与地质》2009,23(4):329-334

在分析切特未斯铜（银）矿的地质特征、围岩蚀变特征、矿床成因基础上,通过与典型角砾岩型矿床和典型斑岩型矿床矿化特征、蚀变特征进行对比,认为该矿床成因类型为斑岩型。根据此类型矿床找矿标志和控制因素,结合区域地质条件研究对比,初步分析了找矿方向,圈定找矿远景区．  相似文献   

山西省代县滩上一带隐爆角砾岩地球物理和地球化学特征及其地质意义     

侯彦明  王云章  徐永婧  张雪梅 《现代地质》2019,33(4):727-737

隐爆角砾岩型金矿是国内外一种具有重要经济价值的矿床类型。在分析山西代县滩上隐爆角砾岩区的金多金属矿床地质背景、地球物理及地球化学特性的基础上,研究滩上一带隐爆角砾岩的岩石化学特征,发现该区金多金属矿体赋存部位位于岩体内、内外接触带及四集庄组岩组捕虏体中。研究认为,金多金属矿由石英斑岩中硫化物局部富集形成,其主要物质来源与滩上岩体之岩浆期后热液有关,黄铁矿化隐爆角砾岩为容矿岩石,断裂及其次级断裂、裂隙等构造活动为金矿体的形成提供了良好的导矿通道,燕山期中酸性浅成-超浅成岩浆活动为研究区成矿提供了大量含矿热液和成矿物质。  相似文献   

龙门山造山带早期断裂活动的古地震制约——来自汶川科钻(WFSD)岩心的证据   总被引：2，自引：0，他引：2  

王焕  李海兵  乔秀夫  司家亮  何祥丽 《岩石学报》2017,33(12):3973-3988

强地震是断裂活动的表现形式,可以诱发地表沉积层序顶部未固结的软沉积物发生变形,形成新的变形层(即震积岩***)。因此,在连续沉积剖面中赋存的多层震积岩应是断裂活动的直接证据。川西前陆盆地中的软沉积物变形记载了龙门山断裂带的活动信息,对认识龙门山造山带演化历史具有重要意义。本文通过"汶川地震断裂带科学钻探"一号孔(WFSD-1)和三号孔(WFSD-3)连续岩心剖面的岩性分析和构造研究,识别出11段不同深度的液化角砾岩层,它们是地震触发成因的软沉积物变形岩层。11个液化角砾岩段厚度从~20m至102m不等,分布在晚三叠世须家河组二-五段。这些液化角砾岩层记录了龙门山前陆盆地形成过程中晚三叠世断裂活动特征及趋势。这些厚度不等的震积岩粗略指示约2~20万年的地震活动长周期(地震幕),以及约4至70万年的间震期(地震幕的间隔时间),反映了龙门山断裂早期脉动式(幕式)活动特征。从不同段液化角砾岩层分布间隔规律来看,地震活跃期间隔(即间震期)越来越短,显示龙门山造山带断裂活动越来越强的趋势。结合前人地表软沉积物变形研究,我们认为龙门山造山带在晚三叠世经历了多期次的正断-逆冲活动的造山作用(至少经历14个地震活跃期),形成龙门山雏形及前陆盆地。  相似文献   

云南省腾冲市小龙河锡稀土多金属矿田新知及其稀土矿的发现   总被引：1，自引：1，他引：0       下载免费PDF全文

李建忠  陆生林  吴文贤  丁俊  王保弟  赵作新  崔子良 《中国地质调查》2017,4(2):9-13

通过对云南省腾冲市小龙河地区古永复式岩体原生构造、蚀变和矿化的类比、对比,结合构造地球化学、年代学研究和初步预查,新发现与之有关的热液弥散状蚀变、侵入角砾岩和大型稀土金属矿体,并伴生稀有金属铷(Rb)、铌(Nb)和稀散金属镓(Ga),存在晚期同岩浆断裂。花岗蚀变岩独居石、锆石和未蚀变黑云钾长花岗岩锡石、锆石U-Pb年龄分别为(75.61±0.47)Ma、(75.68±0.72)Ma、(76.3±3.2)Ma和(77.29±0.54)Ma,年龄相近,反映它们可能是岩浆晚期同构造活动的产物。  相似文献   

青藏高原东部碳酸岩-正长岩杂岩体型REE矿床成矿模式——以大陆槽REE矿床为例   总被引：8，自引：3，他引：5  

刘琰  陈超  舒小超  郭东旭  李自静  赵海璇  贾玉衡 《岩石学报》2017,33(7):1978-2000

冕宁-德昌稀土(REE)矿带位于青藏高原东部,受川西一系列走滑断裂控制,大陆槽矿床是矿带中唯一位于南部的大型REE矿床。在前人研究基础上,结合近年来对整个稀土矿带地质填图和室内研究,重点对大陆槽矿床的成矿特征、赋矿围岩及其蚀变、矿石类型、成矿流体来源和流体包裹体演化等方面与同一矿带内的其它矿床进行了详细对比,进一步总结了碳酸岩型(含碳酸岩-正长岩杂岩体)REE矿床的成矿过程。大陆槽矿床的No.1号和No.3号矿体均位于碳酸岩-正长岩杂岩体内,分别由不同隐爆角砾岩筒所控制。以往研究认为两个矿体的碳酸岩-正长岩杂岩体侵位的年龄都在12Ma左右,本次研究发现在26.49±0.63Ma已经存在碳酸岩-正长岩杂岩体岩浆活动。大陆槽REE矿床受隐爆角砾岩构造活动和风化作用的影响,矿石类型以角砾岩型和风化型为主,脉石矿物和矿石矿物在手标本尺度和镜下很难辨认。通过野外观察、镜下矿物共生组合、包裹体显微测温等研究发现,大陆槽矿化过程和牦牛坪矿床相似,只是矿化规模较小,矿化阶段分为岩浆岩阶段-伟晶岩阶段(600℃)-高温热液阶段(450~350℃)-低温热液阶段(350℃),氟碳铈矿形成于热液阶段的晚期。根据伟晶岩阶段至热液阶段氟碳铈矿中流体包裹体的特征,发现多期次隐爆角砾活动导致大气降水和碳酸岩中脱出的CO_2的加入,使得成矿流体的密度(0.732~0.631g/cm~3)、压力(2436~101bar)逐渐降低,直至成矿。此外,岩相学观察和拉曼测试分析也表明包裹体从熔融包裹体过渡到含重晶石、萤石、天青石子晶的富CO_2包裹体、气液两相包裹体,显示了成矿流体由岩浆至热液的转化过程。大陆槽矿床中的包裹体阴离子以SO_4~(2-)为主,气体以CO_2为主,成矿流体中阳离子主要为K~+、Na~+、Ca~(2+)、Sr~(2+)、Ba~(2+)和稀土元素阳离子,表明流体属于SO_4~(2-)-CO_2-H_2O体系,与矿带中其它矿床的成矿流体体系一致。成矿流体的主要成分是岩浆水、大气水和碳酸岩脱碳作用形成的CO_2,后者导致热液方解石和氟碳铈矿的O同位素(氟碳铈矿和方解石:δ~(18)O=5.8‰~12.5‰)值升高。已有研究显示矿带中不同矿床的脉石矿物如重晶石、天青石的Sr-Nd-Pb同位素与碳酸岩-正长岩杂岩体的相关数值基本一致,表明这些脉石矿物来源于碳酸岩-正长岩杂岩体。多期次隐爆角砾岩化作用及大陆槽断裂相关的构造活动促进了成矿流体的循环,直接或间接导致了大陆槽隐爆角砾岩型和风化型矿石的形成。尽管在大陆槽和牦牛坪矿床可以识别出表生氧化阶段,但这一过程并不伴随稀土矿化,热液阶段才是稀土沉淀的主要阶段。研究还强调了碳酸岩发育的大陆槽No.3矿体和里庄矿床主要出现的霓长岩化与矿化无关,而牦牛坪矿床地表并无霓长岩化蚀变。在以往和本次研究的基础上,建立了川西碳酸岩-正长岩型稀土矿床的成矿模式。  相似文献   

Breccia-cored columnar rosettes in a rubbly pahoehoe lava flow,Elephanta Island,Deccan Traps,and a model for their origin     

Hetu Sheth  Ishita Pal  Vanit Patel  Hrishikesh Samant  Joseph D&#x;Souza 《地学前缘(英文版)》2017,8(6):1299-1309

Rubbly pahoehoe lava flows are abundant in many continental flood basalts including the Deccan Traps. However, structures with radial joint columns surrounding cores of flow-top breccia (FTB), reported from some Deccan rubbly pahoehoe flows, are yet unknown from other basaltic provinces. A previous study of these Deccan “breccia-cored columnar rosettes” ruled out explanations such as volcanic vents and lava tubes, and showed that the radial joint columns had grown outwards from cold FTB inclusions incorporated into the hot molten interiors. How the highly vesicular (thus low-density) FTB blocks might have sunk into the flow interiors has remained a puzzle. Here we describe a new example of a Deccan rubbly pahoehoe flow with FTB-cored rosettes, from Elephanta Island in the Mumbai harbor. Noting that (1) thick rubbly pahoehoe flows probably form by rapid inflation (involving many lava injections into a largely molten advancing flow), and (2) such flows are transitional to ‘a’ā flows (which continuously shed their top clinker in front of them as they advance), we propose a model for the FTB-cored rosettes. We suggest that the Deccan flows under study were shedding some of their FTB in front of them as they advanced and, with high-eruption rate lava injection and inflation, frontal breakouts would incorporate this FTB rubble, with thickening of the flow carrying the rubble into the flow interior. This implies that, far from sinking into the molten interior, the FTB blocks may have been rising, until lava supply and inflation stopped, the flow began solidifying, and joint columns developed outward from each cold FTB inclusion as already inferred, forming the FTB-cored rosettes. Those rubbly pahoehoe flows which began recycling most of their FTB became the ‘a’ā flows of the Deccan.  相似文献   

Morphology of rubbly pahoehoe (simple) flows from the Deccan Volcanic Province: Implications for style of emplacement     

Raymond A. Duraiswami  Ninad R. Bondre  Shreyas Managave 《Journal of Volcanology and Geothermal Research》2008

Lava flows with preserved bases and brecciated upper crusts constitute a morphological type that differs in character from typical pahoehoe and a'a: such flows have been reported from many provinces around the world. Previous studies had referred to these flows informally as ‘pahoehoe flows with rubbly tops’, ‘broken-top pahoehoe’ and ‘rubbly pahoehoe’. Recent studies have formally applied the latter term to describe parts of the well-studied Laki flow in Iceland as well as flows from the Columbia River Basalt province. Rubbly pahoehoe flows are abundant in the upper stratigraphic formations of the Deccan Volcanic Province (DVP), and are more commonly known as simple flows. This study presents detailed observations of such flows from various parts of the DVP and discusses their implications for understanding flow emplacement. These flows, which appear to be single units at the outcrop-scale, are generally much thicker and significantly more extensive than individual pahoehoe lobes that dominate the lower formations of the Deccan stratigraphy. They are characterised by preserved, gently undulating tachylitic bases but variably disrupted crustal zones that grade into flow-top breccias. The breccias are constituted of highly vesicular and oxidised fragments of varying sizes that appear to have been derived from previously formed pahoehoe crusts. Previous work has indicated that the morphology of these flows might be related to initial inflation, accompanied by rapid volatile exsolution and an increase in effusion rate and/or viscosity with time. This agrees reasonably well with the qualitative and quantitative models of emplacement developed for the Laki flow. The abundance of such flows in the upper formations of the Deccan stratigraphy clearly hints at a significant shift in the nature of the Deccan eruptions; this could be indicative of higher eruption rates during this period. This, in turn, raises the possibility of hazardous impact on the climate during the eruption of these flows, which is also discussed in the paper.  相似文献