碳酸岩型稀土矿床成矿流体演化机制研究现状及展望

与碱性岩有关的碳酸岩型内生稀土矿床在中国乃至世界上轻稀土资源储量中占有极为重要的地位,诸如我国内蒙古的白云鄂博稀土矿床、川西冕宁—德昌稀土成矿带中的牦牛坪、大陆槽等稀土矿床、山东微山县郗山稀土矿床以及美国的Mountain Pass稀土矿床等都属于这种类型的稀土矿床.当前,对于这类稀土矿床的成矿流体演化机制,学界主要存...     

安徽五河地区岩浆岩及构造对金矿的控制作用

为研究五河地区金矿床与岩浆岩、构造之间的内在关系,通过重磁异常推断隐伏岩体的分布特征,研究岩浆岩与金矿床的空间分布关系、成矿流体的同位素特征以及郯庐断裂带对金矿床的控制作用.结果显示金矿床大多位于已知岩体或隐伏岩体的边缘,区内各矿床的成矿流体相似,H-O同位素图解中石英样品点大部分落入岩浆水范围,部分落入变质水范围.岩浆岩为金矿成矿提供了重要的物质来源,岩浆的侵入引起了变质岩系的活化,两者形成的混合流体为金元素的运移和富集提供了热源,在金矿和形成过程中活化了金元素,成矿流体沿主干断裂的NNE—NE向次级断裂运移、富集、成矿.     

大火成岩省的成矿效应

大火成岩省(LIPs)是地质历史上重大的地质事件,巨量的岩浆堆积形成了丰富的矿产资源.按照成矿作用与LIPs事件的关系,将其划分为两种类型:①成矿作用与LIPs事件直接相关,两者时间一致或者成矿作用稍晚,该类型矿床可以作为LIPs的组成部分;②成矿作用与LIPs事件在时间上有明显的间断,但与LIPs有间接的成因联系.与...     

入井工作液顺序接触煤岩储层损害实验评价

致密煤岩具有高毛管压力和比表面积大等特点,在钻井、完井和增产改造过程中,流体侵入将造成储层损害,显著降低工程技术效果。以往文献仅报道了单项工作液对煤岩储层的损害,忽视了工作液顺序接触煤岩储层损害的叠加效应。以川南煤田古叙矿区上二叠统龙潭组煤样为研究对象,开展了流体之间配伍性实验、钻井完井液与压裂液顺序接触煤样对渗透率损害实验。单项工作液储层损害评价实验结果表明,压裂液对储层的损害最严重,钻井完井液次之;工作液配伍性和顺序接触损害评价实验结果表明,与钻井完井液接触后,瓜胶压裂液损害最严重,离子平衡压裂液次之,活性水压裂液较轻,清洁压裂液最轻。顺序损害实验反映了工程实际过程,为入井流体评价和优选提供理论依据,有利于促进煤层保护和煤层气高效开发。     

井下瞬变电磁法在巷道底板含水性探测的应用

某矿井目前主要开采山西组煤,为保证下部太原组煤的安全开拓,需查明其底板的水文地质条件。根据该矿井的地质条件,采用井下瞬变电磁法小线框的工作方式,在一采区-530m水平及其以上相关大巷及17煤首采工作面两顺槽内布置6条测线进行探测。在资料解释中,通过设定2级异常阀值对井下富水性进行评价,查明了巷道底板的含水性。经验证,资料处理解释结果与实际揭露地质构造对应良好。     

区域控矿断裂带的航空高光谱遥感技术研究——以黑石山-花牛山深大断裂带为例

利用引进的CASI/SASI/TASI成像光谱系统在甘肃北山柳园-方山口地区获得了3500km2的高空间、高光谱分辨率遥感数据。应用该数据对柳园-方山口地区十余种矿化相关蚀变进行了精细矿物填图,根据蚀变矿物与断裂构造的空间关系,可以区分出成矿构造与非成矿构造。将识别出的成矿构造进行组合,可以得到研究区的成矿构造格架,再将该区已知矿床(点)分布图与其叠合,可以看出:该区已知矿床(点)明显受成矿构造格架控制。深入分析发现,其中黑石山-花牛山大断裂带为成矿构造格架的主干构造。该断裂带在遥感图像上呈"之"字形,通过对受该断裂控制的岩浆岩的岩性识别,确认其为一条深切硅镁壳的深大断裂带。断裂带的EW段在岩浆活动期间被拉张,造成花岗岩类-超基性岩浆的侵入,为成矿提供了重要的物源和热源。在成矿期黑石山-花牛山深大断裂带扭动方向发生了反转,由成岩期的右行变为左行,EW区段由拉张变为挤压,造成成矿热流体上升和对含矿地层的改造,有利于多金属矿床的形成。通过建立航空高光谱遥感找矿模型并开展模式找矿,在柳园-方山口地区新发现了7处多金属矿的找矿靶区(金3处,镍1处,钨钼1处,铜钼1处,铅银1处)。上述研究说明,航空高光谱遥感技术可以从一个新的角度来研究区域控矿断裂带及其成矿作用,并以新的思路和方法指导区域找矿工作。     

小秦岭镰子沟金矿床地质特征、黄铁矿原位硫同位素组成及成因意义

镰子沟金矿床位于华北陆块南缘小秦岭金矿矿集区西部,矿体赋存于太华群上部岩层内,受断裂构造和石英脉控制,带状钾长石化是矿床典型的围岩蚀变,矿物组合为石英-黄铁矿-方铅矿-黄铜矿±重晶石±磁铁矿。为了探讨成矿物质来源及矿床成因,采用LA-MC-ICP-MS技术对镰子沟金矿床黄铁矿进行原位微区硫同位素分析,获得单颗粒黄铁矿的硫同位素变化范围为-15.27‰~-11.98‰,平均-13.35‰,小于共生重晶石硫同位素值9.8‰~12.4‰。根据硫化物与共生硫酸盐矿物,估算成矿热源总硫值为-3.6‰,与新太古界太华群和燕山期华山花岗岩均不同。综合矿化蚀变、地球化学及同位素组成,认为太华群对金矿床成矿物质来源的影响较华山花岗岩明显,但非主要来源,金矿床成矿与深部流体或隐伏岩体有关,矿床受深部流体和构造控制,深部仍有寻找构造蚀变型或微细浸染型金矿体的潜力,但规模有限。     

Ore genesis of the Tianbaoshan carbonate-hosted Pb–Zn deposit,Southwest China: geologic and isotopic (C–H–O–S–Pb) evidence

The Tianbaoshan Pb–Zn deposit, part of the Sichuan–Yunnan–Guizhou (SYG) Pb–Zn metallogenic province, is located in the western Yangtze Block and contains 2.6 million tonnes of 10–15 wt.% Pb + Zn metals. Ore bodies occur as vein or tubular types and are hosted in Sinian (late Proterozoic) carbonate rocks and are structurally controlled by the SN-trending Anninghe tectonic belt and NW-trending concealed fractures. The deposits are simple in mineralogy, with sphalerite, galena, pyrite, chalcopyrite, arsenopyrite, freibergite, and pyrargyrite as ore minerals and dolomite, calcite, and quartz as gangue minerals. These phases occur as massive, brecciated, veinlet, and dissemination in dolostone of the upper Sinian Dengying Formation. Hydrogen and oxygen isotope compositions of hydrothermal fluids range from –47.6 to –51.2‰ and –1.7 to +3.7‰, respectively. These data suggest that H₂O in hydrothermal fluids had a mixed origin of metamorphic and meteoric waters. Carbon and oxygen isotope compositions range from –6.5 to –4.9‰ and +19.3 to +20.2‰, respectively. These compositions plot in the field between mantle and marine carbonate rocks with a negative correlation, suggesting that CO₂ in the ore-forming fluids had multiple sources, including the Permian Emeishan flood basalts, Sinian-to-Permian marine carbonate rocks, and organic matters in Cambrian-to-Permian sedimentary rocks. Sulphur isotope compositions range from –0.4 to +9.6‰, significantly lower than Cambrian-to-Permian seawater sulphate (+15 to +35‰) and sulphate (+15 to +28‰) from evaporates in Cambrian-to-Permian strata, implicating that the S was derived from host-strata evaporates by thermal–chemical sulphate reduction. ²⁰⁶Pb/²⁰⁴Pb, ²⁰⁷Pb/²⁰⁴Pb, and ²⁰⁸Pb/²⁰⁴Pb ratios range from 18.110 to 18.596, 15.514 to 15.878, and 38.032 to 39.221, respectively, which plot in field of the upper crust Pb evolution curve, unlike those of Proterozoic basement rocks, Sinian dolostone, Devonian-to-Permian carbonate rocks, and the Permian Emeishan flood basalts, implying complex derivation of Pb metal in the ore-forming fluids. Geological and isotopic studies of the Tianbaoshan Pb–Zn deposit reveal that constituents in the hydrothermal fluids were derived from multiple sources and that fluid mixing was a possible metallogenic mechanism. The studied deposit is not distal magmatic–hydrothermal, sedimentary exhalative (SEDEX), or Mississippi Valley (MVT) types, rather, it represents a unique ore deposit type, named in this article the SYG type.     

Origin,characteristics and distribution of fault‐related and fracture‐related dolomitization: Insights from Mississippian carbonates,Isle of Man

Viséan limestones on the Isle of Man host numerous examples of fault‐controlled and fracture‐controlled dolomitization, which have been investigated to determine their macro‐scale to micro‐scale characteristics, geofluid origin, timing and relation to basin evolution. Geobodies composed of fabric destructive, ferroan, non‐planar dolomite range from several centimetres to >300 m wide and tens to hundreds of metres long parallel to faults and/or fractures; they have sharply defined margins, cross‐cut stratigraphy and locally finger out along beds or bed boundaries for tens of metres. Larger geobodies accompany NNE–SSW extensional faults with substantial breccia zones. One of these bodies hosts a sphalerite‐rich breccia deposit cemented by dolomite. Saddle dolomite lines or fills vugs and fractures within dolomite geobodies, and is a minor late diagenetic phase in undolomitized limestones. Replacive dolomite has low matrix porosity owing to non‐planar texture and associated cementation, and there is no evidence for subsequent leaching. Three dolomite stages are discriminated by texture, cathodoluminescence petrography and electron microscopy. Disseminated ‘Dolomite 1’ is substantially replaced and may be residual early diagenetic dolomite. Pervasive ‘Dolomite 2’ and ‘Dolomite 3’ have overlapping carbon–oxygen–strontium isotopic and fluid‐inclusion characteristics that indicate precipitation from allochthonous, high‐temperature (98 to 223°C) and high‐salinity (15 to 24 wt% NaCl eq.) brines. These variably equilibrated with host limestones and mixed with resident pore fluids. Overlying mudrocks formed a seal for ascending fluids. Integration of data from the mineral deposit suggests that fault‐fracture systems tapped different deep‐seated fluid reservoirs at different temperatures, and implies fluid interactions with both metamorphic basement and sedimentary cover in large‐scale circulation systems. This phenomenon probably took place during Mesozoic rifting, although an earlier event at the end of the Early Carboniferous cannot be discounted. In either case, a transient heat flow anomaly, previously unrecognized in the Irish Sea region, may be required to account for the hottest fluids.     

金矿成矿流体特点及深-浅部流体相互作用成矿机制

以中国一些典型金矿研究资料为基础 ,结合前人关于深部流体研究成果 ,分析对比了金矿成矿流体和深部流体的特点 ,总结了深部流体参与金矿成矿作用的主要表现 ,然后计算了深部富气流体的能量传递效应和富水流体在不同深度上的密度变化规律。认为深部富气流体主要是向浅部输送大量热能和部分有利于成矿的物质 ,而浅部富水流体下渗提供足够的水体 ,二者在中地壳的“低速层”附近交汇 ,发生相互作用并作用于围岩 ,在有利条件下演化形成成矿流体 ,最终上升到地壳浅部沉淀成矿。