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1.
个旧-大厂地区地质构造演化及锡多金属成矿 总被引：21，自引：0，他引：21
个旧-大厂锡多金属矿床不是简单的燕山晚期地台环境的“花岗岩岩浆期后气液矿床”，矿区地处三大板块的交接部位附近的个旧-大厂锡矿，前泥盆纪区域构造岩浆活动及锡多金属成矿作用强烈，泥盆纪-三叠纪裂谷作用和锡多金属成矿特点突出。泥盆纪受北西向同沉积断裂控制，在南丹-河池一带裂谷作用明显，发生了海底喷流成矿，加上印支-燕山期构造岩浆改造，形成了大厂锡矿。三叠纪受北东向个旧-兴义-晴隆同沉积断裂控制，在个旧、兴义一带发生的裂谷作用，伴随基性火山成矿、喷流热水沉积成矿和燕山晚期花岗岩改造(叠加)成矿，从而形成了个旧锡矿。 相似文献
2.
云南个旧锡多金属矿床处于滇东南锡矿带的西端,是全球最大的锡多金属矿床之一。锡石作为个旧锡矿床中最主要的矿石矿物,其矿物化学特征对矿床成因具有重要的指示意义。本文运用扫描电镜、电子探针等手段对个旧锡多金属矿床中6种不同类型矿石中的锡石进行了详细的内部结构和矿物化学特征研究,并对其可能的成因进行了探讨。扫描电镜研究结果发现,除层间氧化矿型锡石较破碎外,其余类型锡石内部均发育有明显的环带结构。电子探针分析结果显示：各类型矿石中锡石的SnO2质量分数变化范围为97.700%~101.728%;Ta2O5、FeO、ZrO2、HfO2平均质量分数较高,指示锡石形成于高温热液环境;（Fe+Mn）/（Nb+Ta）显示个旧锡矿区各类型矿石中的锡石具有热液锡石的特征,且各类型锡石中Nb2O5和MnO的质量分数极低,说明成矿热液可能来自于高度分异的花岗质岩浆,而Nb、Ta质量分数说明成矿作用发生于酸性-弱酸性环境中;In2O3质量分数显示了成矿温度及压力从块状硫化物型矿石、矽卡岩型矿石、电气石细脉带型矿石、含锡白云岩型矿石到层间氧化矿型矿石有逐渐降低的趋势;云英岩型矿石中锡石的In2O3质量分数较高还需进一步论证。锡石形成过程中岩浆热液物理化学条件的变化导致其内部环带结构的形成,电子探针数据显示锡石的环带结构中化学成分呈"锯齿状"变化,显示成矿作用发生于动荡的环境中,说明锡石沉淀具有多期多阶段的特征。 相似文献
3.
S. M. Aleksandrov 《Geochemistry International》2010,48(12):1220-1236
The boron, tin, tungsten, beryllium, and fluorite deposits of the York Range, Seward Peninsula, represent the continuation
of the Asian segment of the Pacific ore belt and are globally conjugate with the Verkhoyan-Chukotka ore province of Northeastern
Russia. They are localized in the alteration aureoles of dolomites and limestones of the Paleozoic Port Clarence Formation
at the contact with the Mesozoic leucocratic granites and genetically belong to the magnesian-skan ore formation. Ore-generating
process developed in marbles, skarns, and greisens under hypabyssal conditions in several stages and was accompanied by sequential
formation of polymineral assemblages. Early mineralization is represented by magnetite in prograde pyroxene skarns after dolomites.
Postmagmatic ore stage is represented by formation of endogenous borates, including their tin-bearing Mg-Fe species, in the
magnesian skarns, superposition of calcareousskarn assemblages containing calcium borates, borosilicates, and scheelite, formation
of cassiterite and wolrframite in the greisenized granites, and precipitation of sulfides, chrysoberyl, and fluorite. The
mineral composition of the rocks and ores was formed under the influence of F-bearing hydrothermal solutions, which caused
the presence of fluorine in borates, rock-forming silicates, and the replacement of calcite by fluorite. Boron, tin, beryllium,
and fluorine participate at all the stages of endogenous process, but the mineral modes of their occurrence are varied, which
is confirmed by data on their chemical composition. The results of studying the skarns and ores of the Alaska deposits are
of great applied and scientific significance, and can be used for study of skarn-greisen deposits localized at the contacts
of carbonate rocks with granite intrusions of the Pacific ore belt and other world’s regions. 相似文献
4.
华南是我国重要的钨锡成矿区。本文围绕华南与花岗岩有关的大规模钨锡成矿作用,系统收集了区内130余个主要矿床的地质和同位素年代学资料,初步总结了与花岗岩有关大规模钨锡矿床的主要类型和时空分布特征。统计结果表明,矽卡岩型和石英脉型是华南最重要的钨成矿类型,而矽卡岩型和锡石硫化物型(或碳酸盐岩交代型)是华南最主要的锡成矿类型。华南与花岗岩有关钨锡成矿作用具有多时代特点,但大规模成矿均集中于燕山期。以南岭和赣北成矿带为主要代表的钨成矿作用主要集中爆发于晚侏罗世至早白垩世早期(160～120Ma),而右江盆地晚白垩世(110～80 Ma,峰期为90～80 Ma)和南岭成矿带晚侏罗世(160～150 Ma)锡矿床则共同构成了华南最主要的锡成矿作用。多种不同矿化或金属类型在同一矿床或矿田尺度上组合产出是华南与花岗岩有关钨锡矿床的重要特征之一,对指导找矿具有重要意义。对此,文章结合华南地区近年来的一些重要成矿机制研究成果和找矿勘查进展,分别以瑶岗仙、川口、茅坪、柿竹园、大厂和个旧等矿床或矿田为例,论述了华南与花岗岩有关大规模钨锡成矿作用的几种成矿模式和找矿方向。此外,本文在钨、锡成矿花岗岩的岩石学、地... 相似文献
5.
The Gejiu tin-copper polymetallic ore field, located at the westernmost end of the Cathaysia Block in South China, is one of the largest tin polymetallic ore fields in the world. It is associated with magmatic-hydrothermal ore-forming processes triggered by deeply seated structures and concealed granites. The Bi-dimensional empirical mode decomposition (BEMD) was used to decompose gravity data covering an area including the Gejiu tin-copper polymetallic ore field in the west and the Bozhushan silver-lead-zinc polymetallic ore field in the east, which yielded three two-dimensional intrinsic mode function (BIMFs) images and one residue (Res(m, n)) image that depict four layers of geological architectures at different wavelengths within the study area. The high-pass filtered gravity component image (BIMF1) is interpreted to depict the shallow geological architecture, which indicates that the skarn alteration and tin-copper mineralization with positive gravity anomalies are distributed around the granites characterized by negative gravity anomalies. The band-pass filtered gravity component image (BIMF2) is interpreted to depict the middle-shallow geological architecture, which indicates that the outcropped granites in the western Gejiu ore field bounded by the Gejiu fault may extend to the eastern Gejiu ore field to form one integrated granitic complex in the subsurface. The other band-pass filtered gravity component image (BIMF3) is interpreted to depict the middle-lower geological architecture, which indicates that there may be an EW-trending granite zone with negative gravity anomaly at middle-lower depth connecting the Gejiu tin-copper polymetallic field to the Bozhushan silver-lead-zinc polymetallic field, displaying the existence of an EW-trending regional polymetallic ore-forming zone within the study area. The low-pass filtered gravity component image (Res(m, n)) is interpreted to depict the lowest geological architecture within the study area, which reflects that there may be a pair of the NW-trending uplift zone of the mantle and/or the basement with positive gravity anomaly and the depression zone of the mantle and/or the basement with negative gravity anomaly. The Gejiu tin-copper polymetallic deposits and the related granites are located at the transitional zone between the uplift and depression, whereas the Bozhushan silver-lead-zinc polymetallic deposits and the related granites are situated within the depression zone, which implies that the diversity of the Late Yanshanian granites and the related polymetallic deposits in the study area may be controlled by the complexity of the crust-mantle interaction at depth. 相似文献
6.
Recent studies have revealed that the Makeng Fe deposit is a skarn type deposit. However, the skarns in Makeng, occurring primarily between limestone and sandstone, are not typically associated with limestone and plutons. Different periods of intrusions, e.7. Hercynian mafic intrusions and Yanshanian (i.e. early Cretaceous) Dayang–Juzhou granitic intrusion, occurred in the Makeng deposit district. In this study, the formation processes of the skarns and Fe mineralization are constrained by detailed fieldwork, petrology, geochronology, and geochemistry. Skarns and Fe mineralization intersecting the Hercynian mafic intrusions are observed in consecutive specimens from the 106# tunnel. They suggest that the skarn formation and Fe mineralization occurred after the Hercynian mafic intrusions and are related to the later Yanshanian Dayang–Juzhou granitic intrusion. The geochronological characteristics of weakly skarn‐altered diabases, the decreasing nature of Fe contents in altered diabase, and the major element compositions of pyroxenes and garnets also support that Hercynian mafic intrusions are strongly reformed by Yanshanian granitic magmas and the Fe migrated from mafic intrusion was responsible for formation of iron ore. 相似文献
7.
云南个旧锡矿的玄武岩成矿 总被引：20，自引：2，他引：18
个旧锡矿产于个旧东区,是一个以锡铜为主的超大型多金属矿床,具有火山沉积成矿的某些特征。因遭受燕山期花岗岩的叠加改造,区内个旧组卡房段中玄武岩遭受强烈的变质,它又具有花岗岩热液成矿的特征。区内玄武岩的地质地球化学特征表明,印支期玄武岩中的Sn、Cu、Pb、Zn、Ag和Au的质量分数大多数高于世界玄武岩平均值的若干倍;矿石硫化物的硫同位素δ34S为-1.5‰~4.0‰,平均+0.207‰,在幔源硫附近;铅同位素模式年龄分为两组：第一组为180~240 Ma,反映了印支期的火山沉积成矿作用;第二组为80~140 Ma,反映了燕山期花岗岩的叠加改造成矿作用。区内印支期玄武岩为个旧锡铜多金属矿床的形成提供了主要的成矿物质,与成矿有直接联系。 相似文献
8.
Daizo ISHIYAMA Ryoji SATO Toshio MIZUTA Yohei ISHIKAWA Jingbin WANG 《Resource Geology》2001,51(4):377-392
Abstract: The Anle Sn‐Cu and Huanggangliang Fe‐Sn deposits have been exploited in the Linxi district, which is located 165 km northwest of Chifeng City in northern China. In this study the formation mechanisms of the tin deposits in the Anle and Huanggangliang mining area were investigated to understand the mechanisms of tin mineralization in northern China. The veins of the Anle deposit are divided into cassiterite–quartz–chlorite veins, chalcopyrite‐bearing quartz veins, cassi–terite–chalcopyrite–bearing quartz veins and sphalerite‐quartz veins. The sequence of mineralization is tin mineralization (stage I), copper mineralization (stage II), and lead‐zinc mineralization (stage III). The Huanggangliang tin deposit consists of magnetite skarn orebodies and many cassiterite‐bearing feldspar–fluorite veins and veinlets cutting the magnetite orebodies. The fluid inclusions in quartz and fluorite in ores from the Anle and Huanggangliang tin deposits are divided into two‐phase fluid inclusions, vapor‐rich fluid inclusions and poly‐phase fluid inclusions. The final homogenization temperatures of fluid inclusions of quartz in the ores of the Anle deposit and fluorite of tin‐bearing feldspar veins in the Huanggangliang tin deposit range from 195 to 425C and from 215 to 450C, respectively. The fluids responsible for the Anle and Huanggangliang tin deposits were of very high temperature and NaCl‐rich ones containing K, Ca, Al, Si, Ti, Fe and Cl in addition to ore metals such as Sn and Cu. The temperature and chemical composition of fluid in fluid inclusions of igneous rocks in the mining area are very similar to those of fluid in fluid inclusions in the ores of these deposits. The fluid for these ore deposits had a close relation with the fluid coexisting with melt of Late Jurassic granitic rocks in this mining area. Salinities of fluid inclusions from these ore deposits and granitic rocks in the mining area were estimated to range from 35 to 50 wt % NaCl equivalent. Based on arsenopy‐rite geothermometry and fluid inclusion studies, a fluid containing 40 wt% NaCl (eq.) could be formed by phase separation of fluid having 6 wt% NaCl (eq.) at a temperature of 420 to 500C and a pressure of 0.3 to 0.4 kb. The temperatures and pressures presented above indicate an NaCl‐rich magmatic fluid derived from granitic melt that had intruded into a shallow level of crust caused the Sn–Fe–Cu mineralization of the mining area. The geological relationship between these ore deposits and granitic bodies around the ore deposits, and the similarity of fluids forming these ore deposits and coexisting with granitic melt, suggest that these ore deposits were formed by the activity of fluid derived from granitic melt in Late Jurassic age. 相似文献
9.
个旧矿床不仅是一个超大型的锡矿床,同时也是大型的铜、铅、锌、钨和银矿床,此外还伴生众多的有色金属和稀有金属矿产。近些年来,除了成矿与燕山期花岗岩成矿有关的认识外,还有海底喷流成矿和玄武岩成矿的新观点。笔者在参与国家"十五"科技攻关课题《大型锡矿山接替资源探查技术与示范》工作中,通过野外调查和矿床地质特征的总结分析,提出了个旧超大型矿床的成矿模式,个旧矿区成矿作用的主要因素是燕山期含矿花岗岩,与碳酸盐建造和富含成矿物质的岩层发生相互作用,在花岗岩体的内外接触带附近,富集形成一系列锡铜多金属矿床,成矿作用围绕含矿花岗岩而进行。个旧矿区成矿花岗岩与碳酸盐建造和富含成矿物质的岩层以及构造的有利配置是控制矿床空间分布的根本原因。 相似文献
10.
《International Geology Review》2012,54(11):1020-1039
The Shizhuyuan deposit is the largest among the economically important polymetallic tungsten deposits in China. The deposit occurs within the thermal aureole of Yanshanian felsic intrusions that were emplaced into Devonian carbonates and marls. The mineralization can be divided into three phases that are genetically associated with three episodes of granitic emplacement-pseudoporphyritic biotite granite, equigranular biotite granite, and granite porphyry. During the emplacement of pseudoporphyritic biotite granite, thermal metamorphism and subsequent skarnization developed around the stock. The pure limestone was transformed to marble, whereas marls and argillite interlayers were changed to a series of metamorphic rocks such as grossular-diopside hornfels, wollastonite hornfels, diopside hornfels, wollastonite-vesuvianite hornfels, muscovite-K-feldspar-anorthite hornfels, and prehnitevermiculite hornfels. Because of the subsequent strong skarn development, most hornfelses later were transformed into skarns. The skarns distributed around the granite stock are mainly calcic. They are massive in structure, and are composed mainly of garnet, pyroxene, vesuvianite, and wollastonite, with interstitial fluorite, scheelite, and bismuthinite. Although there is no cassiterite in the early skarns, their tin contents average 0.1%. The distribution and compositional and mineralogical relationships of skarn minerals suggest that they formed as a result of progressive reactions of a hydrothermal solution with a limestone of generally constant composition, and that the dominant process was progressive removal of Ca and addition of other constituents to the rocks. Following the primary skarn formation, some of the assemblages were retrograded to new assemblages such as fluorite-magnetite-salite rock, magnetite-fluorite-amphibole rock, and magnetite-fluorite-chlorite rock. The retrograde alteration of the skarns is characterized by a progressive addition of fluorine, alkali components, silica, tin, tungsten, and bismuth. A zonation from garnet-pyroxene skarn or garnet skarn, through fluorite-magnetite-salite rock, to magnetite-fluorite-chlorite rock frequently can be recognized in the deposit. All retrograde-altered rocks contain scheelite, cassiterite, molybdenite, and bismuthinite. During the emplacement of equigranular biotite granite, skarn veins several tens of centimeters wide were developed; they contain large crystals of garnet and vesuvianite, and interstitial scheelite, wolframite, cassiterite, and molybdenite. This second stage of mineralization occurs predominantly as coarse and fine stockwork greisens, which were superimposed on the massive skarns and surrounding marble. Such W-Sn-Mo-Bi-bearing greisens can be divided into topaz greisen, protolithionite greisen, muscovite greisen, and margarite greisen. Besides calcic skarn veins and greisens, manganese skarn veinlets also were developed; they consist of rhodonite, spessartine-almandine solid solution, spessartine, and helvite. The distribution of greisens is responsible for a metal zonation—i.e., W-Sn-Mo-Bi and Sn-Be-Cu-F zones from the contact boundary between the granite stock and skarns outward in the deposit. A third stage of mineralization is represented by lead-zinc veins, which also are accompanied by manganese skarns consisting of spessartine, rhodonite, manganese-rich pyroxene, helvite, tephroite, fluorite, tourmaline, and manganese-rich phlogopite. 相似文献
11.
The Gejiu (个旧) deposit is a superlarge tin-copper polymetallic ore-forming concentration area characterized by excellent metallogenic geological settings and advantageous ore-controlling factors. The deposit displays diverse mineralization properties due to different minerals and mineral deposit types. Based on the principal metallogenic factors, metallogenic mechanisms, mineralized components, and occurrence of mineral deposits or ore bodies, the Gejiu mineral district can be divided into 2 combinations of metallogenic series, 4 metallogenic series, 8 subseries, and 27 mineral deposit types. Spatial zonality is evident. The distribution regularity of the elements in both plane and section is Be-W, Sn (Cu, Mo, Bi, Be)-Sn, Pb, Ag-Pb, Zn around a granitic intrusion. The metallogenic epoch is mainly concentrated in the late Yanshanian. During this period, large-scale metallogenic processes related to movement caused by tectonics and magmatism occurred, and a series of magmatic hydrothermal deposits formed. The ore-forming processes can be divided into 4 stages: the silicate stage, the oxide stage, the sulphide stage, and the carbonate stage. Based on the orderliness and diversity (in terms of time, space, and genesis) of the mineralization, the authors have developed a comprehensive spectrum of ore deposits in the Gejiu area. This newly proposed diversity of mineralization and the spectrum developed in this work are useful not only for interpreting the genesis of the Gejiu deposit but also for improving mineral exploration in the area, and in particular, for finding large deposits. 相似文献
12.
K. Sato 《Mineralium Deposita》1980,15(3):327-334
The occurrence of fluorite deposits in Japan is limited in the provinces characterized by tin and tungsten mineralization within Southwest Japan. The deposits were formed near acidic igneous rocks of Cretaceous to Tertiary age. The ores in limestone are generally associated with skarn and metallic ore minerals such as cassiterite, scheelite and chalcopyrite. Granitic rocks in the provinces are the ilmenite-series (Ishihara, 1977) having enhanced fluorine contents and high initial strontium ratios. A reducing condition of the ilmenite-series granitic magma may have been more favorable for the concentration of fluorine in the residual magma because of the crystallization of relatively Fe-rich mafic minerals. Presence of thick crust bearing carbonaceous matter at the site of magmatism could have involved in the enrichment of fluorine as well as the reducing condition. 相似文献
13.
Abstract: The skarns and genesis were studied of the Huanggang Fe‐Sn deposit and the nearby Sumugou Zn‐Pb deposit in Inner Mongolia, China. In the Huanggang mine, Nos. 1 to 4 Fe ore bodies are arranged along a calcareous horizon from proximal to distal in this order to a granite intrusion named Luotuochangliang, while Sn ore body is situated near another granite intrusion named 204. According to the distance from the granitic intrusions, mineral assemblages in skarns are systematically changed. Garnet is the most predominant skarn mineral throughout the deposit. Hastingsitic amphiboles, however, predominate in the proximal skarns. Fluorite is common in the proximal skarns, while instead calcite is common in the distal skarns. Chlorite is characteristically present only in No. 3 ore body, and chlorite geothermometry gives near 300C for the mineralization of later stage. When garnet crystal shows zonal structure, isotropic andraditic garnet occupies the core, and is surrounded with anisotropic less‐andraditic garnet. The presence of white skarn along the boundary between main skarns and host sedimentary rocks confirms relatively reducing environment prevailing as a whole in the studied area. However, the compositional relation between coexisting garnet and clinopyroxene demonstrates that relatively oxidizing condition was achieved for garnet skarn and magnetite ore in the distal, Nos. 2 to 4 Fe ore bodies and Sumugou deposit, compared to that for garnet skarn in the proximal, No. 1 and Sn ore bodies. Preliminary study on the tin content of garnets in the studied area revealed a certain degree of contribution brought from granitic intrusives since the early stage of skarn formation, irrespective of proximal or distal. Oxygen isotope study on garnet, magnetite, quartz and skarn calcite, as well as hydrogen isotope study on hastingsitic amphibole, demonstrates mainly meteoric water origin for the skarn– and ore‐forming solutions. The occurrence of Sn, W, Mo and F minerals indicates that those elements were mainly supplied to the deposit later than the formation of skarns and iron ores, overlapping to them. These constraints allow to delineate the formation model of the deposit as follows (Fig. 10): At the time of late Jurassic to early Cretaceous, felsic activity occurred in this region as a part of Yanshanian magmatism, and formed granitic intrusions as well as thick volcanic piles on the surface. The circulation of meteoric water was provoked by the heat brought by the intrusions. By this circulation, much amount of iron was extracted from andesites of the Dashizhai Formation, and precipitated as skarns and magnetite ores along calcareous horizons near the bottom of the Huanggangliang Formation. Subsequently, volatile‐rich fluids with Sn, W and Mo were expelled from the solidifying granitic magmas, and precipitated these metals in the pre‐existing skarns and ores. 相似文献
14.
青海西部祁漫塔格地区主要矽卡岩铁多金属矿床成矿地质背景和矿化蚀变特征 总被引：8，自引：2，他引：6
青海西部祁漫塔格地区矽卡岩铁多金属矿床分布广泛,目前已成为中国西部最重要和最有找矿潜力的矽卡岩铁多金属成矿带.在大地构造上,该地区属东昆仑造山带;成矿主要与印支期(204～237Ma)闪长岩、花岗闪长岩和二长花岗岩有关;控矿地层包括蓟县系狼牙山组大理岩、硅质岩,奥陶系-志留系滩间山群大理岩、碎屑岩、硅质岩、中-基性火山岩和石炭系结晶灰岩、碎屑岩等.区内发育3类矽卡岩,即钙矽卡岩、镁矽卡岩和锰质矽卡岩,以前者为主.钙矽卡岩常伴生Fe、Cu、Mo(Pb,Zn)矿化,镁矽卡岩主要伴生Fe矿化,锰质矽卡岩则伴生Pb、Zn(Ag)矿化;矿石矿物组合多种多样,矿化具有一定的分带性.内接触带侵入岩广泛发育钾长石化,与矽卡岩类型一起构成该类矿床的重要找矿标志之一. 相似文献
15.
16.
与超大型锡矿床相关的花岗岩熔融实验结果及其成矿学意义 总被引：1，自引：0，他引：1
在６００～８５０℃，７５～３００ＭＰａ条件下对与个旧超大型锡（多金属）矿床密切相关的个旧复式花岗岩体，和与大厂长坡－铜坑、龙头山２个超大型锡（多金属）矿床密切相关的龙箱盖复式花岗岩体进行系统的实验研究。其结果表明，不仅形成这２个著名复式花岗岩的岩浆性质及岩浆的演化规律有明显的差异，而且形成同一个复式岩体的岩浆的性质及其演化特点亦有明显的不同。个旧花岗岩浆中，形成老卡岩体的岩浆固相线位置低，具有共结岩浆性质，而形成马松、龙岔河岩体的岩浆固相线位置稍高，具有近共结花岗岩浆的特点；形成龙箱盖复式花岗岩的岩浆在性质上有所不同，其固相线位置较高。这些研究结果表明，２类超大型锡矿床的成矿花岗岩浆的性质、起源与演化规律存在明显的差异，这些差异可能是造成这２个复式花岗岩体在超大型锡矿床形成过程中所起的作用不同的重要原因之一。 相似文献
17.
湘南地区蕴藏着丰富的锡矿资源,锡及锡多金属矿矿床(点)分布广泛,类型复杂,它们的形成除与花岗质侵入岩体直接相关外,同时还受到区域地层和地质构造等因素的共同制约。通过对锡矿的地质背景、分布特征、矿床特征与矿化规律、矿床成因及找矿信息和标志的研究,把湘南地区锡矿的找矿归纳为:"划带、圈区、寻体、定位"的找矿模式,不仅从宏观上提出了或解决了锡矿找矿方向的问题,而且近几年来的地质找矿工作得到了实践应用,并取得了丰硕的找矿成果。 相似文献
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《International Geology Review》2012,54(11):1311-1358
Molybdenum exploration activity in China has accelerated tremendously during the past decade owing to the continuous, increasing demand for Earth resources. China possesses the largest Mo reserves in the world (exceeding 19.6 Mt). The major ore deposits are of porphyry, porphyry–skarn, skarn, vein, and sedimentary types. Porphyry molybdenum deposits contain 77.5% of the Chinese Mo reserves, with lesser amounts in porphyry–skarns (13%), skarns (5.1%), and veins (4.4%). Exploitation of sedimentary-type molybdenum deposits thus far has been uneconomical. The six Mo provinces are in the Northeast China, Yanliao, Qinling–Dabie, middle–lower Yangtze River Valley, South China, and Sanjiang areas. We recognize six ore-forming periods: (1) Precambrian (>541 Ma), (2) Palaeozoic (541–250 Ma), (3) Triassic (250–200 Ma), (4) Jurassic–Early Cretaceous (190–135 Ma), (5) Cretaceous (135–90 Ma), and (6) Cenozoic (55–12 Ma). The abundance of Mo ore deposits in China reflects the occurrence of multiple periods of tectonism, involving interactions between the Siberian, North China, Yangtze, India, and Palaeo-Pacific plates. Precambrian molybdenum deposits are related to Mesoproterozoic volcanism in an extensional setting. Palaeozoic Cu–Mo deposits are related to calc-alkaline granitic plutons in an island arc or a continental margin setting. Triassic Mo deposits formed in the syn-collision–postcollision tectonic setting between the Siberian and North China plates and between the North China and Yangzi plates. Jurassic–Early Cretaceous molybdenum deposits formed along the eastern margin of Asia and are associated with the palaeo-Pacific plate-subduction tectonic setting. Cretaceous Mo deposits are related to high-K calc-alkaline granitic rocks and formed in a lithospheric thinning setting. Cenozoic molybdenum deposits formed in a collision setting between the Indian and Eurasian continents and the subsequent extensional setting. 相似文献
20.
The Gejiu tin-polymetallic deposits in the Western Cathaysia Block of South China comprise the world's largest primary tin district, with a total resource of approximately 300 million metric ton ores, at an average grade of 1 wt percent Sn. Tin polymetallic mineralization occurs in five deposits and has four ore types, i.e., greisen, skarn, stratabound cassiterite-sulfide (mostly oxidized) and vein type ore. In each deposit the orebodies typically occur in an extensive hydrothermal system centered on a shallow Late Cretaceous granitoid cupola. Metal zoning is well developed both vertically and horizontally over the entire district, from W + Be + Bi ± Mo ± Sn ores inside granite intrusions, to Sn + Cu-dominated ores at intrusion margins and farther out to Pb + Zn deposits in the surrounding host carbonate. This zoning pattern is similar to that of other hydrothermal deposits in other parts of the world, indicating a close genetic relationship between magmatism and mineralization. In this paper, we dated thirteen mica samples from all types of mineralization and from the five deposits in the Gejiu district. The ages range from 77.4 ± 0.6 Ma to 95.3 ± 0.7 Ma and are similar to the existing zircon U–Pb age of the granitic intrusions (77.4 ± 2.5–85.8 ± 0.6), indicating a genetic relationship between the mineralization and the intrusions. Geological characteristics, metal zoning patterns and new geochronological data all indicate that the tin-polymetallic ores in the Gejiu district are hydrothermal in origin and are genetically related to the nearby granitic intrusions. It is unlikely that the deposits are syngenetic, as has been proposed in recent years. 相似文献