Contrasting fluid inclusion characteristics of staniferous and non-staniferous pegmatites of Southeast Bastar, Central India     

Dipak C. Pal  M.K. Panigrahi  B. Mishra 《Journal of Asian Earth Sciences》2006,28(4-6):306-319

Tin and rare metal-bearing granitic pegmatites in the Bastar–Malkangiri pegmatite belt of Central India are hosted by metabasic and metasedimentary country rocks. Fluid inclusion studies were conducted in spatially associated two-mica granite and the staniferous and non-staniferous pegmatites to characterize the physicochemical environment of mineralization, to distinguish different pegmatites in terms of their fluid characteristics and to envisage a possible genetic link between the pegmatites and spatially associated granite. Three different types of primary inclusions were identified. The type-I, aqueous bi-phase (L+V) inclusions are the most abundant and ubiquitous. Type-II polyphase (L+V+S) inclusions are rare. Type-III, monophase (L) and metastable aqueous inclusions, though less abundant than type-I inclusions, are ubiquitous. The fluid evolution trends indicate that mixing of two different fluids of contrasting salinities, one of high salinity (20–30 wt% NaCl equivalent) and another of low salinity (0–10 wt% NaCl equivalent), was responsible for precipitation of the bulk of the cassiterite. This mixing is the single most important characteristic that distinguishes the staniferous pegmatites from their non-staniferous counterparts. The non-staniferous pegmatites, on the other hand, are typified by the presence either of a high saline or a low saline fluid that evolved through simple cooling. The minimum pressure–temperature of entrapment, estimated from the intersections of the halide liquidus with the corresponding inclusion isochores of type-II inclusions, range between 2.1–2.2 kb and 300–325 °C. The similar P–T range of fluid entrapment of the staniferous and non-staniferous pegmatites indicates that they were possibly emplaced within a similar physical environment. Type-I inclusions from granite recorded only the high salinity fluid, the salinity of which compares well with that of the highly saline fluid component of type-I inclusions in the pegmatites. This is a possible indication of a genetic link between the pegmatites and spatially associated granite.  相似文献   

印度尼西亚西爪哇地区金矿典型矿床     

杨广全  王外全 《云南地质》2007,26(3):284-288

西爪哇金矿位于印度尼西亚西角湾火山岩金、铅锌铜多金属成矿带,该区有众多金矿床(点)。出露的三叠系火山岩地层,以火山喷发沉积为主,岩性组合为安山岩、英安岩、流纹岩及火山角砾岩,具爆发-喷溢沉积的特点,总体表现为火山弧特征。断裂构造破碎带是该地区主要控矿、容矿构造。岩石蚀变强烈,硅化与金矿化关系密切。  相似文献   

东川拖布卡金矿地质及成矿年代学   总被引：7，自引：4，他引：7  

李志伟  田敏  刘和林  应汉龙  钱祥贵 《云南地质》2003,22(4):371-381

东川拖布卡金矿是滇中昆阳群地层找矿的重大突破 ,金资源量达大型矿床规模。分褐铁矿型和石英脉型金矿石两类 ,以石英脉型金矿石为主 ,地表为氧化矿石。金矿成矿受中元古界昆阳群美党组及其近NS向脆 韧性剪切带的双重影响和控制。含金石英脉中石英的　4 0 Ar 39Ar法测年结果 :视年龄值在 4 2 38× 10 6 a～ 5 9 93× 10 6 a之间 ;等时年龄为 4 1 2 5× 10 6 a～5 9 34× 10 6 a ;反等时年龄为 4 0 2 4× 10 6 a～ 5 6 2 5× 10 6 a ;反映金的富集主要形成于喜马拉雅期 ,新生古储的特点十分明显。  相似文献   

Internal vein texture and vein evolution of the epithermal Shila-Paula district,southern Peru     

Alain?ChauvetEmail author  Laurent?Bailly  Anne-Sylvie?André  Patrick?Monié  Daniel?Cassard  Fernando?Llosa?Tajada  Juan?Rosas?Vargas  Johann?Tuduri 《Mineralium Deposita》2006,41(4):387-410

The epithermal Shila-Paula Au–Ag district is characterized by numerous veins hosted in Tertiary volcanic rocks of the Western Cordillera (southern Peru). Field studies of the ore bodies reveal a systematic association of a main E–W vein with secondary N55–60°W veins—two directions that are also reflected by the orientation of fluid-inclusion planes in quartz crystals of the host rock. In areas where this pattern is not recognized, such as the Apacheta sector, vein emplacement seems to have been guided by regional N40°E and N40°W fractures. Two main vein-filling stages are identified. stage 1 is a quartz–adularia–pyrite–galena–sphalerite–chalcopyrite–electrum–Mn silicate–carbonate assemblage that fills the main E–W veins. stage 2, which contains most of the precious-metal mineralization, is divided into pre-bonanza and bonanza substages. The pre-bonanza substage consists of a quartz–adularia–carbonate assemblage that is observed within the secondary N45–60°W veins, in veinlets that cut the stage 1 assemblage, and in final open-space fillings. The two latter structures are finally filled by the bonanza substage characterized by a Fe-poor sphalerite–chalcopyrite–pyrite–galena–tennantite–tetrahedrite–polybasite–pearceite–electrum assemblage. The ore in the main veins is systematically brecciated, whereas the ore in the secondary veins and geodes is characteristic of open-space crystallization. Microthermometric measurements on sphalerite from both stages and on quartz and calcite from stage 2 indicate a salinity range of 0 to 15.5 wt% NaCl equivalent and homogenization temperatures bracketed between 200 and 330°C. Secondary CO₂-, N₂- and H₂S-bearing fluid inclusions are also identified. The age of vein emplacement, based on ⁴⁰Ar/³⁹Ar ages obtained on adularia of different veins, is estimated at around 11 Ma, with some overlap between adularia of stage 1 (11.4±0.4 Ma) and of stage 2 (10.8±0.3 Ma). A three-phase tectonic model has been constructed to explain the vein formation. Phase 1 corresponds to the assumed development of E–W sinistral shear zones and associated N60°W cleavages under the effects of a NE–SW shortening direction that is recognized at Andean scale. These structures contain the stage 1 ore assemblage that was brecciated during ongoing deformation. Phase 2 is a reactivation of earlier structures under a NW–SE shortening direction that allowed the reopening of the preexisting schistosity and the formation of scarce N50°E-striking S2-cleavage planes filled by the stage 2 pre-bonanza minerals. Phase 3 coincides with the bonanza ore emplacement in the secondary N45–60°W veins and also in open-space in the core of the main E–W veins. Our combined tectonic, textural, mineralogical, fluid-inclusion, and geochronological study presents a complete model of vein formation in which the reactivation of previously formed tectonic structures plays a significant role in ore formation.  相似文献   

Geologic and geochemical features of the volatile-rich ore fluid and its tracing and dating in the Xuebaoding Beryl-Scheelite Vein Deposit, China   总被引：7，自引：0，他引：7  

曹志敏  郑建斌  李佑国  任建国  徐仕进  王汝成  T.Shoji  H.KANEDA  S.KABAYASHI 《中国科学D辑(英文版)》2002,45(8):719-729

Laser Raman spectrochemical analysis on single inclusion reveals that multi-phase fluid inclusions exist in the Xuebaoding Beryl-Scheelite Vein Deposit. Besides the solid daughter mineral, there are vapor CO₂, liquid CO₂, water-deficient CO₂ and salt water solution from its center to the border. A close study on the fluid inclusion components and carbon, oxygen, helium and argon isotope tracing and dating suggests that the volatile-rich ore fluid might derive from postmagmatic fluid and rare element enrichment is the result of the mixture of the plutonic alkali granite with crustal material.  相似文献   

文峪金矿床505脉矿化特征及构造控矿规律     

王可勇  范永香  高秋斌 《地质与资源》1997,6(4):270-277

505脉总体走向270~310°,呈透镜体状、扁豆状以尖灭再现或尖灭侧现的形式产出.505脉为一典型的具多金属硫化物含金石英脉.含金矿物主要是黄铁矿,其次为方铅矿和黄铜矿.黄铁绢英岩化是金矿化的重要标志.控矿构造有4次脉动,与其对应,505脉分4个成矿阶段,主要是Ⅰ、Ⅱ阶段及Ⅰ、Ⅱ、Ⅲ阶段叠加的部位成矿最好.505脉受一近东西向脆-韧性剪切带控制.矿体主要产于断裂的85~90°走向段和倾角为小于45~50°的缓倾段.这些部位也是多次矿化叠加、矿体厚度大、矿石品位高的部位,这些地段也是工业矿体产出的地段.  相似文献   

斑岩铜矿床研究综述   总被引：14，自引：0，他引：14  

高合明 《地球科学进展》1995,10(1):40-46

综述了板块构造、大地构造单元、区域构造、深大断裂以及地球深部热点与斑岩铜矿床形成关系的研究成果，系统介绍了斑岩铜矿床蚀变矿化分带特征、蚀变矿化物理化学条件、蚀变矿化的热力学研究、斑岩铜矿床中脉体的产状和分布特征以及成因观点，总结了斑岩铜矿床成矿物质来源与矿床成因模式，最后指出了斑岩铜矿床将来应该注意的研究方向。  相似文献   

国际第四纪地质学研究进展   总被引：1，自引：0，他引：1  

周卫建  薛祥煦 《地球科学进展》1995,10(2):136-142

与人类环境关系密切的第四纪地质学在“过去的全球变化”研究中取得了一系列重要进展，主要体现在对末次冰期旋回的高分辨率环境保护的提，高精度分析方法的建立、气候不稳定性的发现与研究以及穿越赤道的南北半球对比研究的开始等。  相似文献   

花岗质岩浆和矿化之间的关系:重要概念和关键特征   总被引：1，自引：0，他引：1  

ZUREVINSKI Shannon  HOLLINGS Pete  周涛发  王世伟 《岩石学报》2017,33(5):1541-1553

最近对与花岗岩相关的锂、稀土金属和贱金属(例如Cu和Mo)矿产需求重新激发了人们对其成矿作用研究的兴趣。本文综述了不同类型花岗质岩石及与其相关的矿床:1)与高分异花岗岩有关的浸染状稀有金属矿化;2)热液型锡和钨矿化(如:矽卡岩型矿床);3)伟晶岩型稀有元素矿化;4)斑岩型矿化。虽然花岗岩和相关矿化作用之间(特别是斑岩系统相对于稀有金属)的联系还没有明确,但最近这些成矿系统的相关研究进展为探讨两者之间的关系提供了条件。本文重点回顾了与花岗岩相关成矿作用的主要特征,以及与不同类型矿化有关的花岗质岩浆的多样性,并论述了不同类型矿床的成矿模式。尽管长英质侵入岩浆系统复杂多样,但近来与这些矿化系统有关的研究进展可望能够作为找矿勘探的指示。地球化学特征可以揭示岩浆系统的氧化还原状态,进而可以判断斑岩系统的成矿潜力,它还可以与其他找矿勘探指标如矿物的同位素和微量元素分析联合使用。本文还讨论了通过熔融包裹体分析,研究微量元素在硅酸盐岩浆与挥发分体系中的行为。  相似文献   

喜马拉雅东段错那洞钨-锡-铍矿床中铍的赋存状态及成因机制初探     

何畅通  秦克章  李金祥  周起凤  赵俊兴  李光明 《岩石学报》2020,36(12):3593-3606

近年来喜马拉雅淡色花岗岩带被认为是稀有金属成矿的有利地区，并已在该区伟晶岩中发现诸多稀有金属矿物。错那洞矿床是该带内发现最早并具有较大规模的钨锡铍（W-Sn-Be）矿床，Be矿化包括伟晶岩型和矽卡岩型，但目前铍元素的赋存状态还没有被清晰地查明。伟晶岩型矿化主要为伟晶岩中晶型较好的绿柱石晶体；而矽卡岩型铍矿化表现形式则复杂多样。Be元素除了赋存于绿柱石、硅铍石、羟硅铍石等含铍矿物中，还可以广泛分布于矽卡岩矿物中。其中，符山石（Be含量：43×10^-6~887×10^-6）和方柱石（Be含量：1333×10^-6~4643×10^-6）是铍元素赋存的主要载体。矽卡岩型矿化与淡色花岗岩有关，岩浆高分异演化使熔体中Be、Sn、W及挥发分逐步富集，在伟晶岩中饱和绿柱石；之后Be元素在F的络合下随出溶流体进入碳酸盐岩，发生水岩相互作用，萤石的析出引起Be-F络合物失稳，导致Be元素的沉淀。含铍矿物种类及成因机制的研究将有助于指导喜马拉雅地区同类型矿化的评价。  相似文献