柴达木地块北缘牛鼻子梁镁铁质-超镁铁质岩体岩石成因与成矿条件   总被引：4，自引：3，他引：1  

凌锦兰  赵彦锋  康珍  姜常义  宋忠宝  赵双喜  王永刚 《岩石学报》2014,30(6):1628-1646

牛鼻子梁岩体位于柴达木地块西北缘。岩体出露面积约8km²,平面形态呈长条状,长轴方向近东西向。锆石LA-ICP-MS U-Pb年龄为367.0±2.0Ma。岩体中堆晶结构、堆晶韵律和旋回发育,属典型的层状岩体。岩浆分异充分,岩石类型丰富。主要岩石类型有斜长二辉橄榄岩、斜长单辉橄榄岩、角闪二辉橄榄岩、角闪橄榄岩、角闪橄榄二辉岩、角闪二辉岩、橄榄二辉角闪石岩、角闪橄榄辉长岩、细粒辉长岩、似斑状辉长岩、暗色辉长岩、辉长岩、淡色辉长岩、石英闪长岩、英云闪长岩。岩浆源区为高镁拉斑玄武质岩浆（MgO=10.8%）,主体岩浆结晶温度为1100~1178℃。岩浆演化过程中主要发生了橄榄石的分离结晶作用,此外还有少量斜长石的分离结晶/堆晶作用。野外地质观察、岩石薄片观察及岩石地球化学特征表明岩体与围岩之间发生了较强的同化混染作用,并且同化混染强度伴随着岩浆演化过程而逐渐增大。大量的同化混染导致岩石化学系列从拉斑玄武质系列转化为钙碱性系列。岩浆源区属亏损型地幔源区。岩体形成的构造环境为大陆边缘裂解环境。从构造环境、原生岩浆、岩体类型、岩浆分异程度、岩浆含水量、同化混染和橄榄石镍含量七个方面来看牛鼻子梁岩体形成镍铜硫化物矿床的潜力很大。  相似文献   

贵州天桥铅锌矿床地球化学特征及其地质意义          下载免费PDF全文

彭红  蔡冰堰  陶平  李明琴 《贵州地质》2014,31(4):256-260272

通过对天桥铅锌矿床常量元素、稀土元素、同位素及微量元素等地球化学特征的分析,研究了天桥铅锌矿床的成矿物质流体来源及成矿过程。研究结果表明：（1）矿石、围岩等的稀土元素组成特点相似。∑REE相对较低,LREE/HREE比值较大,稀土配分曲线呈富轻稀土的右倾型曲线。Eu负异常明显,Ce具弱负异常特征。（2）矿床成矿物质流体多来源。受陆源影响较大,主要来自上地壳,且可能主要来自赋矿地层及围岩;无大洋地壳和原始地幔来源。（3）成矿作用为热液改造成矿。  相似文献   

Determination of Acidolysis Hydrocarbons in Oil/Gas Geochemical Exploration Sample By Gas Chromatograph     

CHEN Weiming  LI Qingxi  XIAO Xilian  ZHANG Qin  DENG Tianlong 《《地质学报》英文版》2014,88(Z1):128-129

正1 Introduction Although a mumerous of papers were reported for the chemcial or instrumental analysis of inorganic elements for the geocheical samples(Sun and Xie,2014;Sun et al.,2014;Rao et al.,2004).However,the analytical methods  相似文献   

地电化学、构造叠加晕法在盲矿预测中的运用     

张振兵  张海  袁月琴  郭佩佩 《云南地质》2014,(2):245-249

通过在贵州威宁凉山铅锌矿区耿家寨矿段深部开展构造叠加晕法、地表厚覆盖区开展地电化学测量实验,预测深部有较好成矿信息,经过钻探工程验证,获得较好的找矿效果,这表明构造叠加晕法、地电化学测量法在岩溶地区及覆盖地区深部寻找盲矿具有很好的作用,值得推广.  相似文献   

http://www.sciencedirect.com/science/article/pii/S1674987113000558     

Yongqiang Qu  Jianguo Pan  Shouxian Ma  Zhiping Lei  Lin Li  Guoli Wu 《地学前缘(英文版)》2014,5(1):127-138

Several stratigraphic breaks and unconformities exist in the Mesoproterozoic successions in the northern margin of the North China Block.Geologic characters and spatial distributions of fve of these unconformities,which have resulted from different geological processes,have been studied.The unconformity beneath the Dahongyu Formation is interpreted as a breakup unconformity,representing the time of transition from continental rift to passive continental margin.The unconformities beneath the Gaoyuzhuang and the Yangzhuang formations are considered to be the consequence of regional eustatic fuctuations,leading to the exposure of highlands in passive margins during low sea-level stands and transgressive deposition on coastal regions during high sea-level stands.The unconformity atop the Tieling Formation might be caused by uplift due to contractional deformation in a back-arc setting,whereas the uplift after the deposition of the Xiamaling Formation might be attributed to a continental collision event.It is assumed that the occurrences of these unconformities in the Mesoproterozoic successions in the northern margin of the North China Block had a close bearing on the assemblage and breakup of the Columbia and Rodinia supercontinents.  相似文献   

华北克拉通南缘太华杂岩组成及演化   总被引：1，自引：4，他引：1  

第五春荣  刘祥  孙勇 《岩石学报》2018,34(4):999-1018

太华杂岩位于华北克拉通南部,其组成复杂,记录了几乎所有早前寒武纪各阶段重要的地质事件;此外,由于其所处特殊地理位置,研究太华杂岩对于华北克拉通早前寒武纪地壳形成和演化、构造单元划分和基底拼合等都具有举足轻重的科学价值。本文综合已有的岩石学、变质作用、地球化学以及同位素年代学等诸多研究工作,得到以下阶段性结论和认识:1)将鲁山地区太华划分为以深成侵入岩为主的片麻岩系和以变质沉积-火山岩为主的表壳岩系;前者形成于中太古代晚期-新太古代早期,后者形成于古元古代晚期。而小秦岭地区太华杂岩中变质深成侵入岩形成时间跨度较大,为中太古代晚期-古元古代早期;而其上覆的火山-沉积岩可与鲁山太华杂岩的表壳岩类比,形成时间亦为古元古代晚期。2)中太古代-新太古代(2.91～2.50Ga)为华北克拉通南部大陆最主要的地壳形成时期。提出太华杂岩在太古宙经历了两期明显的地壳生长时间,一期发生在2.85～2.70Ga,以鲁山太华片麻岩系中的深成侵入岩和斜长角闪岩为代表;另一期发生在～2.50Ga,以小秦岭华山和崤山地区太华杂岩中各类花岗质岩石为代表。3)太华杂岩在所谓的全球陆壳生长"沉寂期(2.45～2.20Ga)"岩浆活动异常发育,推测这一时期的岩石形成于古元古代俯冲-汇聚环境,可能是与华北克拉通南部太古宙陆块和其他陆块汇聚-碰撞相关。4)太华杂岩在古元古代晚期普遍遭受了强烈的变质和变形,其变质程度主体为高角闪岩相,局部可达麻粒岩相,且记录了包含近等温降压退变质片段的顺时针变质作用P-T轨迹,经历了一个漫长的变质演化过程(1.97～1.80Ga),变质作用的时限跨度可达150Myr。5)提出华北克拉通南部曾经为一个统一基底,称之为"南部太古宙地块",此地块形成时间为新太古代末期(～2.5Ga)。该古老陆块经历了如下5个构造-演化阶段:(1)冥古宙-始太古代初始陆核形成;(2)中太古代-新太古代陆壳快速生长;(3)古元古代早期(～2.3Ga)岩浆活动异常活跃;(4)古元古代(2.30～1.97Ga)陆内拉伸-破裂;和(5)古元古代末期(1.97～1.80Ga)陆块最终拼合。  相似文献   

Eclogite origin and timings in the North Qinling terrane,and their bearing on the amalgamation of the South and North China Blocks   总被引：3，自引：0，他引：3  

H. WANG  Y.‐B. WU  S. GAO  X.‐C. LIU  H.‐J. GONG  Q.‐L. LI  X.‐H. LI  H.‐L. YUAN 《Journal of Metamorphic Geology》2011,29(9):1019-1031

The amalgamation of South (SCB) and North China Blocks (NCB) along the Qinling‐Dabie orogenic belt involved several stages of high pressure (HP)‐ultra high pressure (UHP) metamorphism. The new discovery of UHP metamorphic rocks in the North Qinling (NQ) terrane can provide valuable information on this process. However, no precise age for the UHP metamorphism in the NQ terrane has been documented yet, and thus hinders deciphering of the evolution of the whole Qinling‐Dabie‐Sulu orogenic belt. This article reports an integrated study of U–Pb age, trace element, mineral inclusion and Hf isotope composition of zircon from an eclogite, a quartz vein and a schist in the NQ terrane. The zircon cores in the eclogite are characterized by oscillatory zoning or weak zoning, high Th/U and ¹⁷⁶Lu/¹⁷⁷Hf ratios, pronounced Eu anomalies and steep heavy rare earth element (HREE) patterns. The zircon cores yield an age of 796 ± 13 Ma, which is taken as the protolith formation age of the eclogite, and implies that the NQ terrane may belong to the SCB before it collided with the NCB. The ?_Hf(t) values vary from ?11.3 to 3.2 and corresponding two‐stage Hf model ages are 2402 to 1495 Ma, suggesting the protolith was derived from an enriched mantle. In contrast, the metamorphic zircon rims show no zoning or weak zoning, very low Th/U and ¹⁷⁶Lu/¹⁷⁷Hf ratios, insignificant Eu anomalies and flat HREE patterns. They contain inclusions of garnet, omphacite and phengite, suggesting that the metamorphic zircon formed under eclogite facies metamorphic conditions, and their weighted mean ²⁰⁶Pb/²³⁸U age of 485.9 ± 3.8 Ma was interpreted to date the timing of the eclogite facies metamorphism. Zircon in the quartz vein is characterized by perfect euhedral habit, some oscillatory zoning, low Th/U ratios and variable HREE contents. It yields a weighted mean U–Pb age of 480.5 ± 2.5 Ma, which registers the age of fluid activity during exhumation. Zircon in the schist is mostly detrital and U–Pb age peaks at c. 1950 to 1850, 1800 to 1600, 1560 to 1460 and 1400 to 1260 Ma with an oldest grain of 2517 Ma, also suggesting that the NQ terrane may have an affinity to the SCB. Accordingly, the amalgamation between the SCB and the NCB is a multistage process that spans c. 300 Myr, which includes: the formation of the Erlangping intra‐oceanic arc zone onto the NCB before c. 490 Ma, the c. 485 Ma crustal subduction and UHP metamorphism of the NQ terrane, the c. 430 Ma arc‐continent collision and granulite facies metamorphism, the 420 to 400 Ma extension and rifting in relation to the opening of the Palaeo‐Tethyan ocean, the c. 310 Ma HP eclogite facies metamorphism of oceanic crust and associated continental basement, and the final 250 to 220 Ma continental subduction and HP–UHP metamorphism.  相似文献   

滇-黔边境鲁甸沿河铜矿床的发现与峨眉山大火成岩省找矿新思路   总被引：35，自引：1，他引：35  

朱炳泉  常向阳  胡耀国  张正伟 《地球科学进展》2002,17(6):912-917

滇-黔边境鲁甸沿河铜矿床矿化受二叠纪玄武岩最上部古火山口相角砾凝灰岩-气孔状熔岩和上覆宣威组碳泥质层控制。矿石矿物主要为自然铜、氧化铜与辉铜矿。自然铜呈板片状、网脉状、浸染状产出。矿化与阳起石化、沥青化、硅化和沸石化密切相关。在峨眉山大火成岩省寻找沿河式铜矿应关注以下重要问题：①地球化学急变带所确定的岩石圈不连续界面控制了峨眉山玄武岩裂隙式喷发；②古火山口相从苦橄质到安山质高分异岩浆喷发；③火山口环境联系下的贫硫、贫酸根同生热液活动；④富有机质地层中有机-无机相互作用所产生的强还原性环境；⑤脆韧性断裂带的发育导致矿体的进一步富化。  相似文献   

Geochemical anomaly separation by multifractal modelling     

Mrio A. Gonalves  Antnio Mateus  Vitor Oliveira 《Journal of Geochemical Exploration》2001,72(2)

Geochemical anomaly separation using the concentration–area method as applied to two different geological settings in Portugal is investigated. Soil geochemistry data sets were used in both settings. Geochemical surveys were conducted for the exploration of gold mineralisations in quartz veins associated with major shear zones (Arouca, NW Portugal). Similar surveys were also undertaken for V and Ti exploration related to the accumulation of oxide minerals in gabbroic rocks belonging to an exotic oceanic terrane (Mombeja) and to a late calc-alkaline igneous complex (Odivelas), both in SE Portugal. Results have been interpreted using the extensive information available for each area, which includes detailed geological mapping, structural information, whole-rock chemical analysis, and mineralogical data. Anomalous thresholds for each area were computed and compared mainly with whole-rock chemical analyses and mineral chemistry data. In the Arouca area, anomalies at the local scale were identified for Au (630 ppb), As (912 ppm), and Sb (630 ppm), and at a regional scale for As (96 ppm). In the Mombeja area, anomalies at a regional scale were identified for V (88 ppm), Cr (232 ppm), and Ni (76 ppm), and the available results for Odivelas area suggest the existence of local scale V anomalies, whose magnitude is generally above 400 ppm. In the Arouca area, the correlation between these threshold values and grades in rocks is clearly shown, especially by discriminating two different mineralising events. The second, and most important mineralising event is responsible for grades above 1 ppm for Au in the mineralised structures, contrasting with grades below 500 ppb from the first event. The anomalies identified in Mombeja reflect mainly a regional distribution of the outcropping rock types, mainly metagabbros and serpentinised peridotites, with special emphasis on the correlation between V and the gabbroic rocks. The thresholds obtained for each element are always lower than their mean content in the rocks. The Odivelas area shows threshold values for V clearly above the mean rock content, being a consequence of the occurrence of anomalous accumulations of oxide minerals within the gabbroic rocks. In order to overcome data scarcity, a scheme to super-sampling the population by using estimated values with ordinary kriging in the computation of the anomalous thresholds was essayed. These results, albeit needing further validation, gave some indicative references to the economic potential of this area for V mineralisations.  相似文献   

西昆仑造山带中带提热艾力组沉积环境 及物源区构造背景     

杜涛  侯明才  陈琳  张伟  杨伟  康孔跃  李同选 《地质通报》2013,32(5):751-759

西昆仑造山带中带上石炭统提热艾力组为一套浅变质碎屑岩沉积,四周被三叠纪岩浆岩所包围,研究其沉积环境及物源特征对揭示该区构造背景具有重要的意义。通过野外详细的剖面测制、沉积相标志的观察,结合室内岩矿鉴定和地球化学等综合分析,揭示该套碎屑岩具典型的鲍马序列结构特征,岩性成分成熟度低,主要为一套近物源的斜坡重力流沉积,其物源区较为复杂,主要为切割岩浆弧、过渡岩浆弧和再旋回造山带,源区构造环境为大陆岛弧及活动大陆边缘,表现出活动大陆边缘弧后盆地的沉积特点。  相似文献