巴西Paraná和Bahia地区滑石矿床的地质特征与成因模式(英文)

本文总结了巴西两个最重要的滑石产地,Parana和Bahia区中滑石矿床的地质特征,并探讨了这些矿床的可能成因。巴西的滑石在世界滑石储量与产量中占有十分重要的地位。巴西Parana和Bahia区的滑石矿主要产于前寒武纪地体中。尽管该区的滑石具有不同的地质产状,与变质火山岩和变质沉积岩共生的滑石最为重要。其他类型的滑石,如与镁铁质-超镁铁质岩共生的、在花岗岩与白云质大理岩接触带的、在花岗岩体中呈包体或顶垂体状的、则相对不重要。在巴西与岩浆活动有关的滑石矿化主要发生在前寒武纪(Bahia区)和白垩纪(Parana区)。滑石的成因模式主要有两类:一为与岩浆热液有关的热液交代成矿模式,另一是起源于盆地热卤水的变质流体交代成矿模式。其中后一种成因模式可用来解释巴西的大多数大型滑石矿床,同时也适用于其他地区,如中国辽宁和乌拉尔南部的滑石成矿。     

保靖县卡棚黑滑石矿床地质特征

保靖县卡棚沉积型黑滑石矿床,是一种新类型的滑石矿床。钙质黑滑石矿层赋存于二叠系下统栖霞组上段,呈多层韵律出现,含矿4层,厚5.3～26.3m,含滑石14.1～44.07％,属原生贫矿。产于风化带中的黑滑石粘土,是原生矿层风化淋滤后的产物,属风化带富矿。矿石物质组分简单,主要为黑滑石、方解石、石英、蒙脱石等。矿床风化分带清楚。黑滑石被认为是同生沉积后期,海解作用产物,在风化阶段又进一步相对富集。     

石阡二叠纪层状滑石矿地质特征及成因初析

二叠纪层状滑石矿在湘、川两省曾有过报道,在我省尚属首次发现。本文根据野外调查和室内分析研究,对石阡地区二叠纪滑石矿地质特征进行初步分析论述,并结合沉积环境、构造、矿石化学成份及滑石区域分布特点之间的关系,提出该类滑石矿是来自地内深部含高硅、镁(?)热水在较封闭的静水条件下沉积形成的。具有较大的资源潜力和新的找矿意义。     

河南滑石矿地质特征

河南省滑石矿资源丰富,规模巨大。矿带位于华北地台华能沉降带来栾川－薄山陷褶断束北侧,潘河－马超营大断裂和下汤－拐河大断裂之南附近。主要有三带一点：①卢氏中部潘河－铁洞村滑石成矿带;②栾川北部九里沟－天桥沟滑石成矿带;③鲁山下汤－方城独树滑石成矿带;④泌阳台山滑石矿点。总长３００ｋｍ。河南滑石矿的特点是大而贫,但可选性尚佳。目前已形成以民采为主的规模性开采,在方城独树形成了颇有名气的滑石市场。     

四川若尔盖巴西金矿床地质特征及成因

若尔盖巴西金矿床位于陕甘川三角成矿区,产于中三叠统草地群与印支-燕山期闪长岩侵入体的接触过渡部位,按金矿赋存的主要岩性、岩石成因类型及产出特点,本矿床分为侵入体外接触带交代(硅化)石英岩型和接触带夕卡岩型两种类型。巴西金矿床的形成经历了成岩成矿期、热液期和表生期三期成矿作用,以热液期为主(包括金-毒砂-黄铁矿-石英阶段和金-辉锑矿-方解石阶段)。根据矿石矿物组合,矿物自然连生组合及标型元素特征提供的成矿信息,该文论述了金的运移形式和金的成矿作用机制,探讨了本区两种类型金矿床金矿化的成因。     

永平水泄铜矿床地质特征及其成因

水泄铜矿床受构造和地层岩性控制，热液成矿标志明显。根据矿化分布、矿石结构构造、围岩蚀变、地层中微量元素特征、矿床的同位素组成及流体包裹体等的研究，论证了成矿物质主要来源于兰坪盆地内的沉积岩；成矿流体具热卤水性质；矿床在成因上与喜马拉雅早期古地热活动有关，为一种新的改造型铜矿床。     

保靖葫芦磷矿床地质特征及矿床成因

葫芦磷矿床位于古丈背斜南西端,含磷岩系赋存于震旦系陡山沱组下部,总厚度10m、分为A—B—C—D—E—F沉积序列。矿体呈层状,产状稳定,平均厚1m。P_2O_5平均品位氧化矿石为27％;原生矿石为20％,主要由胶磷矿(氟磷灰石)和隐晶石英、以及有机碳和黄铁矿组成。磷矿形成于陆棚至陆坡的静水环境。成矿物质来自海底岩石溶解、地壳深部、海底火山和海洋生物的磷质,它们在盆地中浓缩,在化学和生物化学作用下,磷质局部富集、沉淀成矿。矿床被认为是化学和生物化学沉积成因。     

浙江和平硼矿床地质特征及成因

和平硼矿床属中低温热液交代型。它是我国首次发现的中型硅硼钙石矿床,可直接利用于玻璃工业。矿体赋存于上侏罗统劳村组底部砾岩中,并受其砾岩成分和构造的控制。硼质来源于隐伏花岗闪长岩体,在温度为306～120℃、pH为6.7、Eh为58.63mV的弱酸氧化环境、封闭条件下富集成矿。     

Preservation of aeolian genetic units by lava flows in the Lower Cretaceous of the Paraná Basin, southern Brazil

The Lower Cretaceous geological record of the intracratonic Paraná Basin in southern Brazil comprises a thick succession of aeolian sandstones and volcanic rocks. The intercalation between aeolian sandstone and volcanic floods allowed the preservation of distinct aeolian genetic units. Each genetic unit represents an accumulation episode, bounded by supersurfaces, that coincides with the base of lava flood events. The entire package can be subdivided into a Lower Genetic Unit, which corresponds to aeolian sandstones preserved below the initial lava flows (Botucatu Formation), and an upper set of genetic units, which comprises interlayered aeolian deposits and lava floods (Serra Geral Formation). The Lower Genetic Unit is up to 100 m thick. Its base is composed of ephemeral stream and aeolian sand sheet deposits that are overlain by cross‐bedded sandstones whose origin is ascribed to simple, locally composite, crescentic and complex linear aeolian dunes. Aeolian accumulation of the lower unit was possible as a result of the existence of a wide topographic basin, which caused wind deceleration, and a large sand availability that promoted a positive net sediment flux. The Upper Genetic Units comprise isolated sand bodies that occur in two different styles: (1) thin lenses (<3 m thick) formed by aeolian sand sheets; and (2) thick sand lenses (3–15 m) comprising cross‐bedded cosets generated by migration and climbing of simple to locally composite crescentic aeolian dunes. Accumulation of the aeolian strata was associated with wind deceleration within depressions on the irregular upper surface of the lava floods. The interruption of sedimentation in the Lower and Upper Genetic Units, and related development of supersurfaces, occurred as a result of widespread effusions of basaltic lava. Preservation of both wind‐rippled topset deposits of the aeolian dunes and pahoehoe lava imprints indicates that lava floods covered active aeolian dunes and, hence, protected the aeolian deposits from erosion, thus preserving the genetic units.     

西藏隆子县那穷锑金矿地质特征及找矿前景分析

那穷锑金矿是近年来通过区域地质矿产调查在西藏自治区隆子县新发现的金多金属矿床,其矿化带受断裂构造控制。目前该矿床研究程度相对较低,若对其成矿地质条件、地质特征及找矿潜力等内容进行专门性和系统性研究,可为该矿床的下步找矿勘探工作提供依据。文章通过总结区域成矿地质背景,分析了该矿床地质特征、地球物理与地球化学异常特征、包裹体地球化学特征,并结合遥感地质特征和异常查证开展相关研究工作,结果表明:矿体主要产于上三叠统涅如组中,受东西向次级断裂构造带控制,目前共发现3条破碎蚀变带;土壤地球化学剖面测量工作中,选择了Sb、Au、As、Bi、Cu作为Sb及多金属成矿指示元素,共圈定单元素异常10处,各元素异常套合较好;激电中梯测量共圈定极化体2条,视极化率异常3处;与成矿有关的流体包裹体类型主要为富液包裹体,并推测矿区流体为含微量CO₂、N₂气体的中低温低盐度NaCl-H₂O热液体系。综合分析认为那穷锑金矿区具备优越的成矿条件,具有寻找金多金属矿的潜力。      

Geologic evolution of the Serrinha nucleus granite–greenstone terrane (NE Bahia, Brazil) constrained by U–Pb single zircon geochronology

U–Pb single zircon crystallization ages were determined using TIMS and sensitive high resolution ion microprobe (SHRIMP) on samples of granitoid rocks exposed in the Serrinha nucleus granite–greenstone terrane, in NE Brazil. Our data show that the granitoid plutons can be divided into three distinct groups. Group 1 consists of Mesoarchaean (3.2–2.9 Ga) gneisses and N-S elongated TTG (Tonalite-Trondhjemite-Granodiorite) plutons with gneissic borders. Group 2 is represented by ca. 2.15 Ga pretectonic calc-alkaline plutons that are less deformed than group 1. Group 3 is ca. 2.11–2.07 Ga, late to post-tectonic plutons (shoshonite, syenite, K-rich granite and lamprophyre). Groups 2 and 3 are associated with the Transamazonian orogeny. Xenocryst ages of 3.6 Ga, the oldest zircon yet recorded within the São Francisco craton, are found in the group 3 Euclides shoshonite within the Uauá complex and in the group 2 Quijingue trondhjemite, indicating the presence of Paleoarchaean sialic basement.Group 1 gneiss-migmatitic rocks (ca. 3200 Ma) of the Uauá complex constitute the oldest known unit. Shortly afterwards, partial melting of mafic material produced a medium-K calc-alkaline melt, the younger Santa Luz complex (ca. 3100 Ma) to the south. Subsequent TTG melts intruded in different phases now exposed as N-S elongated plutons such as Ambrósio (3162 ± 26 Ma), Araci (3072 ± 2 Ma), Requeijão (2989 ± 11 Ma) and others, which together form a major part of the Archaean nucleus. Some of these plutons have what appear to be intrusive, but are probably remobilized, contacts with the Transamazonian Itapicuru greenstone belt. The older gneissic rocks occur as enclaves within younger Archaean plutons. Thus, serial additions of juvenile material over a period of several hundred m.y. led to the formation of a stable micro-continent by 2.9 Ga. Evidence for Neoarchaean activity is found in the inheritance pattern of only one sample, the group 2 Euclides pluton.Group 2 granitoid plutons were emplaced at 2.16–2.13 Ga in a continental arc environment floored by Mesoarchaean crust. These plutons were subsequently deformed and intruded by late to post-tectonic group 3 alkaline plutons. This period of Transamazonian orogeny can be explained as a consequence of ocean closure followed by collision and slab break-off. The only subsequent magmatism was kimberlitic, probably emplaced during the Neoproterozoic Braziliano event, which sampled older zircon from the basement.     

Glaciation and tectonics in an active intracratonic basin: the Late Palaeozoic Itararé Group, Paraná Basin, Brazil

The Paraná Basin (1 600 000 km²) is the largest intracratonic basin in southern South America and contains a thick (1300 m) Permo-Carboniferous glacial succession (the Itararé Group). This paper describes over 1700 m of drill core recovered during recent exploration for oil and gas. Itararé Group sediments consist of massive and stratified diamictites interbedded with massive and graded sandstones, and massive and laminated mudstones. Facies are interpreted as the product of sediment gravity flows in a glacially influenced marine basin. Three stratigraphic formations can be defined across the basin, each consisting of a lowermost sandstone-rich member overlain by a diamictite-rich member. Examination of Itararé Group rocks both in core and outcrop shows that depositional processes were influenced by active faulting and downslope resedimentation on relatively steep and unstable substrate slopes. Primary glacial deposits such as tillites and associated striated pavements occur along the present eastern outcrop belt which probably coincided with the eastern basin margin during deposition of the Itararé Group. Ice masses fringing the eastern (southern African) and western (Bolivian) basin margins supplied sediment to the basin in the form of fluvio-glacial deltas, fans and floating ice tongues. This sediment was then resedimented downslope as debris flows and turbidites. Both stratigraphic relationships and the regional distribution of facies types identify a clear pattern of basin subsidence and step-wise expansion by outward faulting within Late Proterozoic mobile belts. The position of successive basin margins can be related to specific lineament structures in the underlying basement. Asymmetric expansion of the Paraná Basin occurred along the northern and southern basin margins during deposition of the Itararé Group; this expansion probably reflects shallow crustal adjustments activated by collisional movements along the Andean margin of South America during the Hercynian Orogeny.     

冀东兴隆一带层状黄铁矿—铅锌矿床的地质特征及其成因

冀东兴隆一带中元古界高于庄组中有一些层状黄铁矿-铅锌矿床,如杨树庄、高板河、杨树台、黄土梁、梓木林、椴木峪和沙窝店(关堂子)等,分布在近东西向长六七十千米的一条线上,它们的地质特征很相似。矿床的成因有争议。一派认为是后生热液交代矿床,选择性交代使矿体依岩层成假象;     

中国滑石矿床的含矿建造类型

本文研究和总结了我国滑石矿床的含矿建造类型,划分出:①超基性岩含滑石建造;②变质的镁质碳酸盐岩含滑石建造;③钙镁质碳酸盐岩含滑石建造;④镁质粘土岩含滑石建造等4种滑石矿床含矿建造。阐述了不同含矿建造的主要特征以及滑石的成矿作用特点,指出了滑石成矿作用的发生与否主要与下列因素有关:①岩石条件;②物质来源;③建造类型和岩石组合类型;④介质条件;⑤构造条件诸因素控制的。     

Multipurpose geochemical maps produced by integration of geochemical exploration data sets in The Paraná Shield, Brazil

Old geochemical datasets from the Paraná Shield of southern Brazil have been integrated into a new geochemical database and the results are presented as a series of multipurpose geochemical maps. Although the 24 datasets retrieved were analysed by three different laboratories, the maps produced correlate surprisingly well with bedrock geological features.The retrieval of old geochemical exploration data sets for the purpose of generating maps showing element depletions and enrichments is a powerful tool with a wide range of applications: trace elements such as Zn, Cu and Mo can significantly affect crop productivity; areas with high abundances of harmful elements such as As and F can be delineated in order to identify public health hazards; heavy metals such as Cd, Pb and Hg can be measured in order to better constrain knowledge of chemical background levels for environmental monitoring. The integration and manipulation of different data sets can however be complicated by the heterogeneity in sampling and analytical procedures.     

石墨矿床分布特征、成因类型及勘查进展

[研究目的]石墨已成为新兴技术产业的重要原材料,也是未来高新技术发展的重要关键性矿产资源.中国既是石墨资源大国,也是生产消费大国,摸清石墨矿产资源分布现状,总结不同成因类型石墨矿床地质特征及成矿规律对保障石墨有效供给具有重要意义.[研究方法]搜集已公开发表或出版的石墨矿产资料,对石墨矿床地质特征、物质来源及成因等内容进...