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1.
Several recent studies have suggested that rocks associated with mineral deposits of hydrothermal origin are generally enriched in Rb. TI is similar in its geochemical characteristics to Rb, but its use as a potential guide to ore deposits has not been suggested. Although TI has the same size and valency as Rb, it is concentrated more in residual melts than Rb and K because the TI-O bond is more covalent and weaker than either the Rb-O or K-O bonds.A new method which is rapid and precise has been developed by one of the authors for the determination of TI in geological materials at the ppb level. About 350 rocks from 4 mineralized areas in northeastern Washington and central Montana were analyzed for TI by this method. Most of these rocks were also analyzed for SiO2, A12O3,Fe2O3, MgO, CaO, Na2O, K2O, TiO2, P2O5, MnO, Ag, As, Au, Ba, Co, Cu, F, Li, Mo, Ni, Pb, Sr, Sb, Sn, Sr, Te, U, W, and Zn. The ore deposits of the areas studied include the gold-silver deposits of the Republic district, the uranium deposit of the Midnite mine, the coppermolybdenum deposit of Mount Tolman, and the gold deposits of the North Moccasin mining district.In all the mineralized areas there is significantly more TI in hydrothermally altered rocks than in unaltered rocks. The very high abundance of TI in the altered rocks of the North Moccasin gold district, and the significant positive correlations of TI and K and TI and Rb in the mineralized rocks of the other three areas suggest that TI was concentrated in hydrothermal fluids. In altered rocks the average K/Rb and K/TI ratios are lower, and the Rb/Sr and TI/Sr ratios are higher.Often the abundance of TI and the K/TI and TI/Sr ratios are more useful in delineating mineralized areas than the abundance of Rb and the K/Rb and Rb/Sr ratios. The ternary relationships between TI and several other elements, especially Rb, K, Ba, and Sr, show mineralized rocks to fall near the TI apices or near the TI-Rb or TI-K boundaries.  相似文献   

2.
Chemical analysis of biotite in representative granitic rocks in Japan shows that the total Al (TAl) content changes with the metal type of the accompanying hydrothermal ore deposits and increases in the following order: Pb‐Zn and Mo deposits < Cu‐Fe and Sn deposits < W deposits < non‐mineralized granitic rocks. The TAl content of biotite in granitic rocks may be a useful indicator for distinguishing between mineralized and non‐mineralized granitic rocks. A good positive correlation is seen between the TAl content of biotite and the solidification pressure of the granitic rocks estimated by sphalerite and hornblende geobarometers and the mineral assemblages of the surrounding rocks. These facts suggest that the TAl content of biotite can be used to estimate the solidification pressure (P) of the granitic rocks. The following empirical equation was obtained: where TAl designates the total Al content in biotite on the basis O = 22. According to the obtained biotite geobarometer, it is estimated that Pb‐Zn and Mo deposits were formed at pressures below 1 kb, Cu‐Fe and Sn deposits at 1–2 kb, W deposits at 2–3 kb and non‐mineralized granitic rocks were solidified at pressures above 3 kb.  相似文献   

3.
错那洞穹隆是北喜马拉雅片麻岩穹隆带(NHGD)中发现的新成员,穹隆由核-幔-边3部分组成。核部由寒武纪花岗质片麻岩组成,幔部由早古生代云母片岩和夕卡岩化大理岩组成,边部由变质沉积岩组成。在穹隆核部后期侵入有淡色花岗岩和伟晶岩脉。祥林铍锡多金属矿位于错那洞穹隆北部,矿区内发育多条南北向、北东向张性断裂。通过系统的地表工程控制,在穹隆幔部和断层破碎带内新发现了铍锡多金属工业矿体。通过错那洞穹隆北部祥林矿区的解剖,矿化类型可初步划分为夕卡岩型、锡石-石英脉型、锡石-硫化物型和花岗伟晶岩型。夕卡岩型矿体赋存在穹隆幔部的夕卡岩化大理岩内,矿化以铍、锡、钨为主,锡品位变化较大。锡石-石英脉型矿体受北东向张性断裂控制,矿化以锡、铍、钨为主,矿石品位相对较富。锡石-硫化物型矿体受大理岩内的层间滑脱构造控制,富锡,而铍、钨相对较贫。伟晶岩型矿体矿化为铍为主,伴生铷等。钻孔深部验证发现夕卡岩型矿体、锡石-硫化物型矿体、锡石-石英脉型矿体深部延伸较稳定。通过岩浆与铍锡多金属成矿作用的关系的研究,提出了祥林矿区两期次铍锡钨多金属矿成矿作用,分别与弱定向二云母花岗岩及白云母花岗岩两期次淡色花岗岩浆活动密切相关。在矿体特征研究和矿床类型总结的基础上,明确了下一步的找矿标志和方向。锡石-硫化物型铍锡多金属矿和锡石-石英脉型铍锡多金属矿铍、锡、钨品位相对较富,为今后主攻的矿床类型。  相似文献   

4.
Petrological characteristics of granitic rocks related to the world large molybdenum deposits are studied. The granitoids are evaluated by Fe2O3+TiO2‐FeO+MnO‐MgO diagrams, and found to all plot to the magnetite‐series field. They are all high silica and high‐K series, but not A‐type, except for the Climax‐type porphyries and some others in the Colorado mineral belt. By‐product molybdenum contained in porphyry copper deposits, lower grade but huge tonnage, occurs with calc‐alkaline I‐type magnetite‐series granodiorite and monzogranite. Felsic intrusive rocks of the Climax mine are A‐type and are exceptionally high in trace elements such as F and Rb, which are generally enriched with W and Sn‐related granitoids that originated in crustal source rocks. The by‐product molybdenites in porphyry copper deposits appear to originate in adakitic granodiorite or monzogranite, having deep origins with the subducted slab or thickened juvenile mafic lower crust. Therefore, there is no single magma type but the magnetite series, which concentrates a large volume of molybdenum in the ore deposits.  相似文献   

5.
The Skellefte district in northern Sweden is host to abundant volcanogenic massive sulphide (VMS) deposits comprising pyritic, massive, semi-massive and disseminated Zn–Cu–Au ± Pb ores surrounded by disseminated pyrite and with or without stockwork mineralisation. The VMS deposits are associated with Palaeoproterozoic upper crustal extension (D1) that resulted in the development of normal faults and related transfer faults. The VMS ores formed as sub-seafloor replacement in both felsic volcaniclastic and sedimentary rocks and partly as exhalative deposits within the uppermost part of the volcanic stratigraphy. Subsequently, the district was subjected to deformation (D2) during crustal shortening. Comparing the distribution of VMS deposits with the regional fault pattern reveals a close spatial relationship of VMS deposits to the faults that formed during crustal extension (D1) utilising the syn-extensional faults as fluid conduits. Analysing the shape and orientation of VMS ore bodies shows how their deformation pattern mimics those of the hosting structures and results from the overprinting D2 deformation. Furthermore, regional structural transitions are imitated in the deformation patterns of the ore bodies. Plotting the aspect ratios of VMS ore bodies and the comparison with undeformed equivalents in the Hokuroko district, Japan allow an estimation of apparent strain and show correlation with the D2 deformation intensity of the certain structural domains. A comparison of the size of VMS deposits with their location shows that the smallest deposits are not related to known high-strain zones and the largest deposits are associated with regional-scale high-strain zones. The comparison of distribution and size with the pattern of high-strain zones provides an important tool for regional-scale mineral exploration in the Skellefte district, whereas the analysis of ore body shape and orientation can aid near-mine exploration activities.  相似文献   

6.
The Sierras Pampeanas orogen, in northwestern Argentina, hosts significant Sn–W mineralization in a variety of mostly epizonal granite stocks emplaced in variably metamorphosed country rocks. The San Blas, Huaco and El Durazno granite stocks in the Sierra de Velasco, the La Quebrada granite in the Sierra de Mazán, the Cerro Colorado granite in the Cerro Negro, and the Los Mudaderos and Sauce Guacho granite stocks in the Sierra de Ancasti, are largely peraluminous (ASI between 1.05 and 1.38) and represent S-type granites, are strongly fractionated (i.e., high Rb–Sr ratio), have a low oxidation state (low Fe2O3/Fe2O3 ratio) and are geotectonically linked to syncollisional magmatism. The U–Pb SHRIMP analyses on zircons from the Cerro Colorado and La Quebrada granites, located in the Cerro Negro and Sierra de Mazán, respectively, revealed ages from Lower Ordovician (Tremadocian) to Carboniferous. All granites display elevated LREE values, low HREE values and negative Eu anomalies. With regards to total REE values, two groups of granite stocks can be recognized. The granites with lower REE contents are highly evolved granites and are related to Sn–W mineralization. The mineralized granites display higher values of Sn, W and Rb, and lower values of Sr and Ba compared to barren granites. These trace element characteristics appear to be diagnostic for Sn–W mineralized granite stocks in the western Sierras Pampeanas. The western Sierras Pampeanas contains locally geochemically evolved Carboniferous granites, which are interpreted to be the main control of significant Sn–W mineralization. The Carboniferous age of western Sierras Pampeanas Sn–W mineralization sets it apart from the Triassic age of the Sn–W mineralization in the Eastern Tin belt of Bolivia.  相似文献   

7.
丹池成矿带是我国重要锡多金属成矿带,过去对丹池成矿带成岩成矿研究主要集中在大厂矿田及五圩矿田,而对丹池成矿带北部的芒场矿田岩浆作用时代、源区特征及其成矿性缺少分析。芒场矿田岩浆活动强烈,发育隐伏斑状花岗岩及有关的花岗斑岩脉和隐伏细粒花岗斑岩及有关的白云母花岗斑岩脉。本文分析花岗斑岩脉U-Pb年龄及花岗斑岩脉和白云母花岗斑岩脉主、微量元素组成,以探讨岩浆活动时代、岩浆源区特征及其成矿潜力。芒场矿田花岗斑岩脉锆石U-Pb年龄为89.1±0.9Ma (MSWD=0.9),和丹池成矿带内大厂矿田岩浆活动时代相近,表明丹池成矿带岩浆活动时代都发生于90Ma左右。白云母花岗斑岩脉具高A/CNK比值(2.69～2.88),含高铝硅酸盐矿物白云母及在Th-Rb图上沿S型花岗岩趋势线分布,和大厂矿田S型黑云母花岗岩的特征基本一致,表明其主要为S型花岗岩。花岗斑岩脉形成时代晚于白云母花岗斑岩脉,但其具有更低的SiO_2含量和更高的MgO、Fe_2O_3~T、CaO和TiO_2含量,且在SiO_2与TiO_2、Fe_2O_3~T、Al_2O_3和P_2O_5关系图中分布于不同区域,没有线性变化关系,显示两者不是同一岩浆结晶分异演化形成的,而为不同沉积变质岩部分熔融形成的。白云母花岗斑岩脉富Al_2O_3、K_2O、Rb、Cs、Sn、W、Nb和Ta,在Rb/Ba-Rb/Sr图上位于富粘土源区,为强风化作用形成的富粘土质富稀有金属源区部分熔融形成的产物。华南西部基底发育经强风化作用形成的富粘土质富稀有金属元素沉积变质源区,为华南西南缘大规模锡矿床的形成提供了物质基础。  相似文献   

8.
The ~2,752-Ma Weld Range greenstone belt in the Yilgarn Craton of Western Australia hosts several Fe ore deposits that provide insights into the role of early hypogene fluids in the formation of high-grade (>55 wt% Fe) magnetite-rich ore in banded iron formation (BIF). The 1.5-km-long Beebyn orebody comprises a series of steeply dipping, discontinuous, <50-m-thick lenses of magnetite–(martite)-rich ore zones in BIF that extend from surface to vertical depths of at least 250 m. The ore zones are enveloped by a 3-km-long, 150-m-wide outer halo of hypogene siderite and ferroan dolomite in BIF and mafic igneous country rocks. Ferroan chlorite characterises 20-m-wide proximal alteration zones in mafic country rocks. The magnetite-rich Beebyn orebody is primarily the product of hypogene fluids that circulated through reverse shear zones during the formation of an Archean isoclinal fold-and-thrust belt. Two discrete stages of hypogene fluid flow caused the pseudomorphic replacement of silica-rich bands in BIF by Stage 1 siderite and magnetite and later by Stage 2 ferroan dolomite. The resulting carbonate-altered BIF is markedly depleted in SiO2 and enriched in CaO, MgO, LOI, P2O5 and Fe2O3(total) compared with the least-altered BIF. Subsequent reactivation of these shear zones and circulation of hypogene fluids resulted in the leaching of existing hypogene carbonate minerals and the concentration of residual magnetite-rich bands. These Stage 3 magnetite-rich ore zones are depleted in SiO2 and enriched in K2O, CaO, MgO, P2O5 and Fe2O3(total) relative to the least-altered BIF. Proximal wall rock hypogene alteration zones in mafic igneous country rocks (up to 20 m from the BIF contact) are depleted in SiO2, CaO, Na2O, and K2O and are enriched in Fe2O3(total), MgO and P2O5 compared with distal zones. Recent supergene alteration affects all rocks within about 100 m below the present surface, disturbing hypogene mineral and the geochemical zonation patterns associated with magnetite-rich ore zones. The key vectors for identifying hypogene magnetite-rich Fe ore in weathered outcrop include textural changes in BIF (from thickly to thinly banded), crenulated bands and collapse breccias that indicate volume reduction. Useful indicators of hypogene ore in less weathered rocks include an outer carbonate–magnetite alteration halo in BIF and ferroan chlorite in mafic country rocks.  相似文献   

9.
本文运用构造解析的方法,结合地层学、岩石学及地球化学等方面的研究,搞清了鞍山地区元古宙岩群的构造变形规律,建立了构造变形序列,探讨了该区韧性变形带的分类性质、形成机制、形成时代以及韧性变形带与构造序列的关系,在此基础上总结出了本区地质构造的演化规律,以及构造变形对铁矿床的控制规律。  相似文献   

10.
Updated aeromagnetic maps of New Mexico together with current knowledge of the basement geology in the northern part of the state (Sangre de Cristo and Sandia–Manzano Mountains)—where basement rocks were exposed in Precambrian-cored uplifts—indicate that the northeast-trending Proterozoic shear zones that controlled localization of ore deposits in the Colorado mineral belt extend laterally into New Mexico. The shear zones in New Mexico coincide spatially with known epigenetic precious- and base-metal ore deposits; thus, the mineralized belts in the two states share a common inherited basement tectonic setting. Reactivation of the basement structures in Late Cretaceous–Eocene and Mid-Tertiary times provided zones of weakness for emplacement of magmas and conduits for ore-forming solutions. Ore deposits in the Colorado mineral belt are of both Late Cretaceous–Eocene and Mid-Tertiary age; those in New Mexico are predominantly Mid-Tertiary in age, but include Late Cretaceous porphyry-copper deposits in southwestern New Mexico.The mineralized belt in New Mexico, named the New Mexico structural zone, is 250-km wide. The northwest boundary is the Jemez subzone (or the approximately equivalent Globe belt), and the southeastern boundary was approximately marked by the Santa Rita belt. Three groups (subzones) of mineral deposits characterize the structural zone: (1) Mid-Tertiary porphyry molybdenite and alkaline-precious-metal deposits, in the northeast segment of the Jemez zone; (2) Mid-Tertiary epithermal precious-metal deposits in the Tijeras (intermediate) zone; and (3) Late Cretaceous porphyry-copper deposits in the Santa Rita zone. The structural zone was inferred to extend from New Mexico into adjacent Arizona. The structural zone provides favorable sites for exploration, particularly those parts of the Jemez subzone covered by Neogene volcanic and sedimentary rocks.  相似文献   

11.
The Southern Great Xing'an Range(SGXR) hosts a number of Early Cretaceous Sn and associated metal deposits, which can be divided into three principal types according to their geological characteristics: skarn type deposits, porphyry type deposits and hydrothermal vein type deposits. Fluid inclusion assemblages of different types of deposits are quite different, which represent the complexities of metallogenic process and formation mechanism. CH_4 and CO_2 have been detected in fluid inclusions from some of deposits, indicating that the ore-forming fluids are affected by materials of Permian strata. Hydrogen and oxygen isotope data from ore minerals and associated gangue minerals indicate that the initial ore fluids were dominated by magmatic waters, some of which had clearly exchanged oxygen with wall rocks during their passage through the strata. The narrow range for the δ~(34)S values presumably reflects the corresponding uniformity of the ore forming fluids, and these δ~(34)S values have been interpreted to reflect magmatic sources for the sulfur. The comparation between lead isotope ratios of ore minerals and different geological units' also reveals that deeply seated magma has been a significant source of lead in the ores.  相似文献   

12.
北大巴山震旦寒武系中铜锌矿特征及找矿前景   总被引：1，自引：0，他引：1  
龚银杰 《地质与勘探》2013,49(1):113-122
北大巴山属南秦岭造山带,在震旦-寒武纪形成一套以深水滞流盆地相为主的硅质炭质碎屑岩夹碳酸盐岩沉积.自开展地质大调查工作以来,该区域发现大量的铜锌矿点.根据矿体赋存位置、成因及矿石类型,铜锌矿可分为韧性剪切带型、石英脉型及岩浆岩接触变质型三种类型.通过对区内铜锌矿成矿规律的总结及成矿条件的分析,认为北大巴山具有良好的矿源层、完善的输导系统、丰富的储矿空间,因而具有较大的找矿潜力.指出深大断裂带附近的庄子沟组中碳酸盐岩为有利的赋矿部位.  相似文献   

13.
The object of this study is to establish the nature of geochemical alteration in the wall rocks of the Selbaie Cu-Zn-Ag deposit, and to ascertain whether bedrock geochemistry could be applied in exploration for deposits of this type. The Selbaie Cu-Zn-Ag deposit, in northwestern Quebec, is atypical of base-metal deposits in the Canadian Shield, as mineralization occurs in epigenetic veins and as disseminations in volcanic wall rocks, rather than as syngenetic massive sulfide bodies which have been the focus of extensive comparable studies in the past. The deposit comprises three mineralized zones in felsic tuffs and quartz porphyry. Two of these, the A1 and A2 zones, which are the focus of the present study consist of quartz-carbonate veins containing chalcopyrite, sphalerite, and pyrite, and accessory sulfide minerals. The B zone is not considered in this study. Samples of drill core were collected from sections crossing the A1 and A2 zones and analyzed for total Si, Al, Fe, Mg, Ca, Na, K, Ti, Mn, P, and S by X-ray fluorescence, and for aqua-regia-extractable Cu, Zn, Ni, Pb, Fe, and Mn by atomic absorption. Although the distribution of individual element concentrations is clearly related to bedrock type, rocks proximal to mineralization have higher SiO2, Fe2O3, Cu, Zn, Fe, and S contents, and lower Al2O3 and K2O contents, than rocks more distal from mineralization. MgO content shows an irregular distribution and may also increase toward mineralization. CaO and Na2O contents are very low in all pyroclastic rocks.In order to take into account the effect of bedrock type, linear regression analysis was performed on the data to estimate the normal concentration of individual elements using SiO2 contents as the predicted variable. Spatial distributions of residual values of element concentrations indicate that rocks close to mineralization have higher residual Fe2O3, Cu, Zn, Pb, and Fe contents, and lower residual Al2O3 and K2O contents, compared to rocks more remote from mineralization. These distribution patterns are clearer than in the case of the single-element data but variations between element responses still exist in some instances. In an attempt to overcome the variation in patterns revealed by some element distributions, discriminant analysis was undertaken to see whether mineralized areas could be distinguished on the basis of an element association. Discriminant functions were calculated for data from areas adjacent to mineralization, and from areas remote from mineralization. Areal distribution of discriminant scores outlined an anomalous area extending up to 200 m beyond the mineralization. Petrographic studies of selected samples correlated high SiO2 and low Al2O3 content with silicification in the most altered rocks adjacent to mineralization. High Fe2O3, MgO, and extractable Fe concentrations were found to occur in chlorite- and carbonate-rich zones. Samples rich in S, Cu, Zn, and b, and to a lesser extent Fe, were characterized by the presence of sulfides. High concentrations of Al2O3 and K2O relative to that of SiO2 are typical of sericitization. On this basis, the results demonstrate that anomalously high or low concentrations of element associations, revealed by discriminant analysis, occur in large coherent zones exceeding the size of the deposit. The procedure is potentially useful as an exploration guide for epigenetic disseminated and vein-type base-metal styles of mineralization as well as the syngenetic massive sulfide type of deposits that have been extensively studied in the past.  相似文献   

14.
The Sangdong scheelite–molybdenite deposit in northeast South Korea consists of strata-bound orebodies in intercalated carbonate-rich layers in the Cambrian Myobong slate formation. Among them, the M1 layer hosts the main orebody below which lie layers of F1–F4 host footwall orebodies. Each layer was first skarnized with the formation of a wollastonite + garnet + pyroxene assemblage hosting minor disseminated scheelite. The central parts of the layers were subsequently crosscut by two series of quartz veining events hosting minor scheelite and major scheelite–molybdenite ores, respectively. The former veins associate amphibole–magnetite (amphibole) alteration, whereas the latter veins host quartz–biotite–muscovite (mica) alteration. Deep quartz veins with molybdenite mineralization are hosted in the Cambrian Jangsan quartzite formation beneath the Myobong formation. In the Sunbawi area, which is in close proximity to the Sangdong deposit, quartz veins with scheelite mineralization are hosted in Precambrian metamorphic basement. Three muscovite 39Ar–40Ar ages between 86.6 ± 0.2 and 87.2 ± 0.3 Ma were obtained from M1 and F2 orebodies from the Sangdong deposit and Sunbawi quartz veins. The Upper Cretaceous age of the orebodies is concordant with the published ages of the hidden Sangdong granite, 87.5 ± 4.5 Ma. This strongly suggests that the intrusion is causative for the Sangdong W–Mo ores and Sunbawi veins.Fluid inclusions in the quartz veins from the M1 and F2 orebodies, the deep quartz-molybdenite veins, and the Sunbawi veins are commonly liquid-rich aqueous inclusions having bubble sizes of 10–30 vol%, apparent salinities of 2–8 wt% NaCl eqv., and homogenization temperatures of 180–350 °C. The densities of the aqueous inclusions are 0.70–0.94 g/cm3. No indication of fluid phase separation was observed in the vein. To constrain the formation depth in the Sangdong deposit, fluid isochores are combined with Ti–in–quartz geothermometry, which suggests that the M1 and F2 orebodies were formed at depths of 1–3 km and 5–6 km below the paleosurface, respectively. The similarity of the Cs (cesium) concentrations and Rb/Sr ratios in the fluid inclusions of the respective orebodies indicate an origin from source magmas having similar degrees of fractionation and enrichment of incompatible elements such as W and Mo. High S concentrations in the fluids and possibly organic C in the sedimentary source likely promoted molybdenite precipitation in the Sangdong orebodies, whereas the scheelite deposition in the deep quartz–molybdenite veins hosted in the quartzite is limited by a lack of Ca and Fe in the hydrothermal fluids. The molybdenite deposition in the Sunbawi quartz–molybdenite veins hosted in the Precambrian metamorphic basement rocks was possibly limited by a lack of reducing agents such as organic C.  相似文献   

15.
Two zoning patterns in tin deposits are proposed according to geochemical environments.
  1. Acidic zoning pattern is characteristic of tin deposits associated with sialic rocks and tin-bearing veins in carbonate rocks. Six zones may be recognized from the granite mass outwards: (1) Nb?Ta?(Li?Be?Mo), (2) Sn, (3) W?(Sn), (4) Cu?Pb?Zn?(Bi), (5) Sb?Hg, and (6) Au?Ag. This kind of zoning is related with the temperature difference involved in the deposition of various ore minerals in an acidic (or neutral) geochemical enviroment. From the granite outwards, the temperature decreases gradually with increasing distance from the heat source.
  2. Alkaline zoning pattern is typical of tin deposits occurring in calcareous and magnesian carbonate rocks. Three zones can be recognized from the granite mass outwards: (1) Cu?Zn?Bi, (2) Sn, and (3) Fe?Pb?Zn?Cu. A calcium-and magnesium-rich alkaline environment is responsible for this zoning pattern. In this case the normal sequence of mineral formation will be greatly changed owing to neutralization when an acidic ore-forming solution enters the alkaline environment.
Zoning structure in tin deposits is very complex and highly variable, depending on: (1) the geochemical environment in which the deposits are formed, (2) the type of shield beds, and (3) the character of ore-forming solutions. However, there are some known examples showing similar zoning patterns for the deposits that are similar in these three aspects.  相似文献   

16.
内蒙古乌努格吐山斑岩型铜钼矿床元素迁移定量探讨   总被引：2，自引：0，他引：2  
元素的富集贫化是矿床中固有的客观规律。在以往相关研究中, 研究者们多从定性的角度对此进行讨论, 定量研究不够系统。本文以内蒙古乌努格吐山斑岩型铜钼矿床为例, 利用Grant方程, 定量探讨了该矿床蚀变围岩中元素的带入、带出特征。结果表明, 不同元素的质量迁移在矿化蚀变范围内表现出一定的规律性, 相对于原岩而言, 各蚀变带中Cu、Mo、Au、Ag、W、Sn、As、F、Hg、S等表现为明显的带入特征, 而CaO、Na2O、TiO2、Zr、Ba、Sr、Rb和REE则表现为明显的带出特征。这些元素的带入带出导致矿床及蚀变围岩中元素的富集贫化。元素质量迁移定量计算思路和方法, 为地球化学勘查向定量化方向发展提供了可行的途径。  相似文献   

17.
Sn–W deposit of the Mueilha mine is one of many other Sn–W deposits in the Eastern desert of Egypt that associated with albite granite. Two forms of Sn–W mineralizations are known at the Mueilha Sn-mine area, namely fissure filling quartz veins and greisen. Cassiterite and/or wolframite, sheelite, and beryl are the main ore minerals in the greisen and quartz veins. Subordinate chalcopyrite and supergene malachite and limonite are also observed in the mineralized veins. To constrain the P–T conditions of the Sn–W mineralizations, fluid inclusions trapped in quartz and cassiterite, have been investigated. The following primary fluid inclusion types are observed: CO2-rich, two-phase (L?+?V) aqueous, and immiscible three-phase (H2O–CO2) inclusions. Low temperature and low salinity secondary inclusions were also detected in the studied samples. Microthermometric results revealed that Sn–W deposition seem to have taken place due to immiscibility at temperature between 260°C and 340°C, and estimated pressure between 1.2 to 2.2 kb. Microthermometric results of fluid inclusions in fluorite from fluorite veins illustrated that fluorite seems to be deposited due to mixing of two fluids at minimum temperature 140°C and 180°C, and estimated minimum pressure at 800 bars.  相似文献   

18.
Granitic rocks obtained during field excursions of the famed mineralized regions of the Erzgebirge, Germany (mainly tin‐bearing), and South China (mainly tungsten‐bearing) have been geochemically analyzed and their results are compared with similar (mainly tungsten‐bearing) granites in the island‐arc setting of Southwest Japan. The studied granitoids all belong to the ilmenite‐series. The collision‐related Erzgebirge granitoids are rich in K2O and P2O5, have high A/CNK ratios (1.11–1.24, i.e. S type), but are also high in Ga/Al ratio (i.e., having some A‐type characteristics). In South China, the Xihuashan granites, in contrast, are very low in P2O5, and have A/CNK slightly above 1.0 (1.01–1.05), indicative of I type granites. The (Sn‐) W‐related granites of southwest Japan have similarly low P2O5 and A/CNK ratios, indicative also of I‐type. Both in the Xihuashan and southwest Japan, the tungsten‐related granites have high whole‐rock δ18O values implying involvement of W‐rich crustal rocks. Sn and W contents of the unaltered granites are lowest in the island‐arc setting where the related Sn–W deposits are smallest in size relative to the collision and continental margin settings of the Erzgebirge and South China.  相似文献   

19.
About 25 economically significant, Kuroko-type massive sulfide bodies lie in a metamorphosed volcano-sedimentary complex (probable Middle Ordovician) known as Tetagouche Group, in Bathurst area, New Brunswick. Despite unresolved structural complexities, it does appear that they were deposited during a particular phase of volcanic activity and are, therefore, contemporaneous. Most of the sulfide bodies are closely associated with iron-rich rocks representing various facies of iron formation, and together with sulfides it constitutes the “ore horizon‘ which, therefore, is highly magnetic. Aero-magnetic and ground-magnetic techniques are useful to locate the ore horizon but problems are created because of the occurrence of iron-rich rocks with no sulfide, along another horizon in the Tetagouche Group.Petrographic and geochemical characteristics of various types of iron-rich rocks have been studied to see if the iron-rich rocks of the ore horizon can be distinguished from the iron-rich rocks of the other horizon. The iron-rich rocks found in the Tetagouche Group can be classified into five types: (1) cherty magnetitic rocks; (2) iron-rich chloritic rocks; (3) sideritic rocks; (4) basic iron formation; and (5) maroon shale. The basic iron formation, which is quite magnetic, gives a false indication of the ore horizon wherein the presence of any of the first three types of rocks is expected. Moreover, the basic iron formation is generally similar in appearance and mineralogy to some of the cherty magnetitic and chloritic rocks.Regarding major element composition, TiO2, Na2O, Al2O3 and CaO are higher whereas Fe2O3, FeO and MnO are lower in the basic iron formation than in the other iron-rich rocks. These geochemical characteristics can help distinguish the barren rocks of the basic iron formation from those of the ore horizon during the exploration programs.  相似文献   

20.
采用岩矿鉴定、扫描电镜和电子探针等手段,对湘南地区多个钨锡多金属矿床的矿化蚀变进行了研究和总结.结果 表明,湘南地区钨锡多金属矿化蚀变矿物组成复杂,但各矿区普遍存在锡石、黄铜矿、黑钨矿(或白钨矿)、闪锌矿、方铅矿等金属矿物,萤石和黄玉常见,云母化、钾长石化、绿泥石化、尖晶石化等热液蚀变普遍,表明成矿流体具有类似或相同的来源及组分;各矿田(或矿床)的成矿流体均富含B和F等挥发分及Fe和Mn,钨、锡和铜矿化密切共生,钨锡多金属矿石中可见Nb和Be矿化,表明Li、Be、Nb、Ta、W、Sn、Bi、Cu、Pb、Zn等矿化为类似成矿流体的产物;初步研究认为湘南地区的钨锡多金属矿化是同一岩浆房分异演化的成矿流体的产物,提出了成矿的概念模型.  相似文献   

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