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1.
微细浸染型金矿深源成矿流体的硅同位素地球化学示踪 总被引：1，自引：0，他引：1
对黔西南和桂西北微细浸染型金矿床围岩,矿石和热液硅化石英的硅同位素组成及硅质阴极发光特征的研究发现,原生硅化石英不发光,而围岩中的石英和次生硅化石英明显发光、与对对应,围岩中石英的硅同位素组成与矿石的热液硅化石英的硅同位素组成也可以明显分开。 相似文献
2.
卢秋霞 《大地构造与成矿学》2000,24(1):75-80
应用阴极发光技术研究了微细浸染型金矿中赋矿围岩和矿石中硅质以及成矿期和表生期石英脉的阴极发光特征。结果表明 :围岩(包括石英斑岩和辉绿岩墙)中的硅质和石英及次生硅化石英均表现不同的发光特征 ,而与原生矿化有关的原生硅化石英不发光 ;其中 ,氧化矿石中的硅化石英和表生梳状石英脉在阴极发光下呈棕色 ,与赋矿围岩中碎屑石英的次生溶解加大边表现的发光特征一致。这表明氧化和表生石英的硅质来源与溶解围岩和改造原生矿石有关 ,而原生硅化石英的硅质来源与围岩(包括岩浆岩)无关 ,进而表明成矿物质并非围岩提供。结合其它方面的系列研究 ,为该类型金矿属深源流体成矿作用产物的新观点 ,即成矿物质和流体可能直接来源于深部或上地幔提供了进一步的证据。这表明 ,阴极发光技术是一种简便、可靠和实用的矿床成因研究手段。 相似文献
3.
Multiple isotope composition (S, Pb, H, O, He, and Ar) and genetic implications for gold deposits in the Jiapigou gold belt, Northeast China 总被引：2，自引：0，他引：2
Qingdong Zeng Zaicong Wang Huaiyu He Yongbin Wang Song Zhang Jianming Liu 《Mineralium Deposita》2014,49(1):145-164
The Jiapigou gold belt (>150 t Au), one of the most important gold-producing districts in China, is located at the northeastern margin of the North China Craton. It is composed of 17 gold deposits with an average grade around 10 g/t Au. The deposits are hosted in Archean gneiss and TTG rocks, and are all in shear zones or fractures of varying orientations and magnitudes. The δ34S values of sulfide from ores are mainly between 2.7?‰ and 10?‰. The Pb isotope characteristics of ore sulfides are different from those of the Archean metamorphic rocks and Mesozoic granites and dikes, and indicate that they have different lead sources. The sulfur and lead isotope compositions imply that the ore-forming materials might originate from multiple, mainly deep sources. Fluid inclusions in pyrite have 3He/4He ratios of 0.6 to 2.5 Ra, whereas their 40Ar/36Ar ratios range from 1,444 to 9,805, indicating a dominantly mantle fluid with a negligible crustal component. δ18O values calculated from hydrothermal quartz are between ?0.2?‰ and +5.9?‰, and δD values of the fluids in the fluid inclusions in quartz are from ?70?‰ to ?96?‰. These ranges suggest dominantly magmatic water with a minor meteoric component. The noble gas isotopic data, along with the stable isotopic data, suggest that the ore-forming fluids have a dominantly mantle source with minor crustal addition. 相似文献
4.
辽宁白云金矿床稳定同位素地球化学特征及矿床成因 总被引：1，自引：0，他引：1
白云金矿床是辽东地区的一个大型金矿床,其成矿物质来源及矿床成因一直存在争议。本文系统地研究了白云金矿床的氢、氧、硫和碳同位素地球化学特征。研究结果显示:成矿流体中δ~(18)OV-SMOW值变化范围为13.5‰15.9‰,δD_(V-SMOW)为-107‰-83‰,表明成矿流体以岩浆水为主;矿石中黄铁矿的δ~(34)S_(V-CDT)为-8.3‰2.9‰,以富轻硫和贫重硫为特征,与辽河群围岩中黄铁矿的硫同位素组成(δ~(34)S_(V-CDT)为7.0‰18.7‰)有明显差异;矿石中方解石的碳同位素δ~(13)C_(V-PDB)为-2.2‰-0.4‰,类似于火成碳酸岩或地幔包体来源的碳同位素特征,也与辽河群大理岩的碳同位素组成明显不同。成矿元素特征对比也显示,成矿物质来源与辽河群没有必然联系。综合矿床地质特征和地球化学特征,认为白云金矿床是与深部岩浆流体活动有关的岩浆热液型金矿床。 相似文献
5.
夏家店金矿床位于南秦岭造山带内,是一个受构造和地层控制的大型金矿床,矿石类型为角砾岩型、碎裂岩型和石英脉型3种类型,赋矿围岩主要为寒武系水沟口组的炭泥质板岩、炭硅质板岩、硅质岩及白云岩,次为泥盆系西岔河组的角砾岩。本文对夏家店金矿床中矿石（角砾状炭硅质板岩、碎裂硅化白云岩、碎裂炭泥质板岩和石英脉状矿化的硅质岩）和围岩（硅质岩、硅化白云岩和硅质板岩）的微量元素、铂族元素（PGE）质量分数进行测试,进而探讨成矿物质来源以及矿床成因。结果表明：不同类型的矿石与其各自的围岩具有高度的相似性,均富集Sr、Ga、Zr等元素;不同类型的矿石稀土总量均高于各类围岩,但是两者具有相似的稀土配分模式,轻稀土富集,重稀土亏损,均表现出负Eu异常（δEu值为0.51~0.63）;不同类型的矿石PGE总量（7.71×10-9~38.30×10-9,平均值23.00×10-9）均明显大于各类围岩PGE总量（1.28×10-9~2.44×10-9,平均值1.86×10-9）,相比上地壳,不同类型的矿石均明显富集Os、Ir、Pt和Pd,亏损Ru、Rh,而各类围岩均富集Os,亏损Pt、Ru、Rh、Pd,但两者的铂族元素配分曲线具有高度相似性,呈Ru亏损的V型,为地壳的（Os）-Pt-Pd型配分模式。以上特征表明不同类型的矿石和围岩具有明显的微量、稀土元素和PGE地球化学继承性,暗示夏家店下寒武统有可能是重要的矿源层之一。同时,所有矿石和围岩的Au/Ir值（分别为4 821~299 666）和406~8 050）及Pd/Ir值（分别为16.9~588.0和15.2~47.5）变化范围均较大,两者Au/Ir值远高于炭质球粒陨石和原始地幔值、Pd/Ir值远高于岩浆成因矿石值,且夏家店金矿床矿石和围岩的PGE配分曲线与典型热液成因矿床一致。这些特征显示夏家店金矿床具有明显的热液成因,是构造-热液流体成矿作用的产物。 相似文献
6.
西准噶尔布兰萨拉地区位于谢米斯台-沙尔布提铜多金属成矿带的西段,区内已发现金矿床、金矿点、矿化点数十处,但目前尚无人对区内的金成矿条件进行系统总结和分析,下一步找矿方向不明确。本文在前人工作基础上,通过收集、整理已有的钻探、槽探、化探等资料,结合实地勘察及样品采集等工作,初步梳理出石英脉型和蚀变岩型两种金矿化成因类型。赋矿地层主要为古生界下志留统谢米斯台组,赋矿岩系为火山碎屑岩,岩性以石英脉、硅化凝灰岩等为主。晚志留世中酸性侵入岩与金矿的关系密切。北东向孟布拉克断裂为研究区内主干断裂,为导矿构造,控制着带内金矿的分布及规模,北东向、近东西向、北北东向的第二级次级断裂是主要的成矿、容矿构造。不同方向构造交汇地段、中酸性侵入体发育地段及金地球化学晕圈分布地段是研究区内下一步金矿找矿方向。 相似文献
7.
哀牢山金矿带成矿流体稀土元素地球化学 总被引：24，自引：2，他引：22
本项研究测定了矿石、蚀变围岩和相应未蚀变岩石的稀土元素组成。通过对这些地质体稀土元素地球化学特征的对比研究发现,在成矿流体的演化过程中,镇沅和墨江两个金矿床成矿流体的稀土模式具明显的变化,而大坪金矿成矿流体的稀土模式则保持相对不变。因此,大坪金矿的稀土模式（轻稀土高度富集、弱负Ｅｕ异常和较强负Ｃｅ异常）可以代表初始成矿流体的稀土模式。研究表明,具有这种稀土模式的流式,可能是由地幔去气作用产生的地幔 相似文献
8.
山东郗山-龙宝山地区与碱性岩有关的稀土矿床地质特征及成因 总被引：1，自引：0，他引：1
郗山和龙宝山稀土矿具有相似的成矿地质背景、控矿岩体特征及矿床地质特征。燕山早期碱性侵入岩与稀土矿关系密切,稀土矿体主要赋存于杂岩体内及其附近围岩中;稀土元素和同位素研究表明,含矿质的富碱岩浆可能属壳幔混源型,碱性岩浆及成矿物质最初可能都来源于上地幔同一部位,而在岩浆上侵过程中同化混染了地壳物质。郗山稀土矿为单一富轻稀土矿床,矿脉类型以含稀土石英重晶石碳酸盐脉为主,含稀土矿物以氟碳铈矿和氟碳钙铈矿为主,碳酸铈钠矿和菱钙锶铈矿属国内首次发现。龙宝山稀土矿为稀土、金共生矿,矿脉类型主要为石英脉和硅化角砾岩;含稀土矿物主要有氟碳铈矿、氟碳铈镧矿、氟碳钙铈矿;金矿物有自然金、银金矿等。成矿时代稍晚于岩浆岩形成时代,属中生代燕山晚期;矿床成因类型为碱性岩浆期后中-低温热液稀土矿床。 相似文献
9.
We discuss the nature of the ore-forming hydrothermal fluid in the Noya gold-bearing calcite-quartz-adularia veins of central Kyushu, Japan on the basis of oxygen, carbon, and strontium isotope ratios, and aqueous speciation calculations for the present-day geothermal fluid. The isotopic values of the Noya ore-forming fluid were estimated to be −6.5‰ for δ13C and −7.5‰ for δ18O. The oxygen isotopic equilibrium temperatures for vein calcite are more than 180°C at the bottom of the Noya mineralization zone, and decrease with increasing elevation. As the temperature decreased, the dominant carbon species in the fluid changed from H2CO3 to HCO3- at about 120°C. The equilibrium temperatures for vein quartz are consistent with the calcite calculations. The carbon and oxygen isotope trends of the Noya vein calcite and the isotope ratios of strontium suggest that the fluids that precipitated the Noya veins were controlled by an andesite-dominated geology. Chondrite-normalized REE patterns for the white-colored veins from wells 51-WT-1 and 51-WT-2 displayed a light REE-rich pattern with positive Eu anomalies, suggesting the existence of a reducing environment for the fluid. The pyrite-rich gray-colored veins and a silicified rock from well 51-WT-2 showed higher REE concentrations than did the white veins. Altered host andesitic rocks have similar REE patterns to that of the silicified rock, and have higher REE contents than the others in the drill cores. Aqueous speciation calculations showed that the fluid in the hydrothermal reservoir is currently in muscovite stability. The fluid at the ore-mineralization stage may have contained more potassium or have had a higher pH, so that adularia precipitated with calcite and quartz, as well as gold. Fluid boiling at depth in the system produced the gold-bearing calcite-quartz-adularia veins. 相似文献
10.
Geology and Origin of the Dongping Alkalic-Type Gold Deposit, Northern Hebei Province, People's Republic of China 总被引：6，自引：0，他引：6
Feng–Jun NIE 《Resource Geology》1998,48(3):139-158
Abstract: The Dongping deposit, located near the center of the northern margin of the north China craton, is one of the largest gold deposits in China. It is spatially, temporally, and genetically associated with the shallowly-emplaced Hercynian Shuiquan-gou alkaline intrusive complex. The complex intrudes high-grade metamorphic rocks of the Archean Sanggan Group along a deep-seated fault zone within the north China craton. Four major ore bodies (Nos. 1, 2, 22, and 70), consisting mainly of a set of en echelon lenses and veins, have been delineated at the Dongping deposit. Hypogene hydrothermal activities can be divided into four periods from early to late including: (1) gold-bearing K–feldspar–quartz stockworks and veins; (2) disseminated sulfide and gold zones; (3) gold-bearing quartz veins, and (4) barren calcite-quartz veins. Individual veins and stockwork systems can be traced along strike for 125 to 600 m and downdip for 100 to 600 m; they range from 0. 5 to 3 m in thickness. The mineralogical composition of the ore in the first three hypogene periods is relatively simple. It is composed of pyrite, galena, sphalerite, magnetite, specularite, chalcopyrite, native gold, electrum, calaverite, and altaite. Gangue minerals include K–feldspar, quartz, sericite, chlorite, epidote, albite, and calcite. Ore grade averages 6 g/t Au, but varies between 4. 14 and 22. 66 g/t Au. Gold is generally fine-grained and not visible in hand specimen. Fluid inclusions in ore-bearing quartz of periods 1, 2, and 3 are CO2–rich, variable salinity (2. 5–21 wt% equiv. NaCl), and have variable homogenization temperatures of 195° to 340°C. Quartz in the gold-bearing K–feldspar–quartz stockworks (period 1), disseminated sulfide and gold zones (period 2), and the gold-bearing quartz veins (period 3) has calculated δ18OH2O values between –1. 7 and 6. 9%, and δ values of fluid inclusion waters between –101 and –66%. All these isotope data of the ore-forming fluids plot between the magmatic fluid field and the meteoric water line. Sulfide minerals disseminated in host rocks show positive δ34S values of 1. 9 to 3. 5%. Pyrite separates from he gold-bearing K–feldspar–quartz stockworks and veins (period 1) have a δ34S range of –4. 3 to 0. 5%, whereas δ34S values of pyrite, chalcopyrite, galena, and sphalerite from the disseminated sul-fide and gold zones (period 2) and the gold-bearing quartz veins (period 3) vary from –5. 3 to –13. 4%. Gold ores are also characterized by relatively radiogenic lead isotope compositions compared to those of the alkaline syenite host rock. The data are interpreted as indicative of a mixing of lead from the alkaline intrusive complex with lead from Archean metamorphic rocks. The combined fluid inclusion measurements, sulfur, oxygen, hydrogen, and lead isotope data, and petrological observations indicate that the Dongping deposit was formed from the mixing of these magmatic fluids with meteoric waters. The deposit is, therefore, believed to be a product of Hercynian alkaline igneous processes within the north China craton. 相似文献
11.
《Ore Geology Reviews》2009,35(4):597-609
The magma–ore deposit relationship of most low-sulfidation epithermal ore deposits is still unclear, partly because many stable isotopic studies of such deposits have indicated the predominance of meteoric waters within hydrothermal fluids. However, it is certainly true that hydrothermal systems are ultimately driven by magmatic intrusions, and epithermal gold deposits might therefore be produced by magmatic activity even in deposits having has no obvious links to a magma. We re-examine the genesis of two typical low-sulfidation epithermal gold deposits, the Kushikino and Hishikari deposits, using structural simulations and isotope data.Many epithermal gold deposits including the Kushikino and Hishikari deposits have been discovered in Kyushu, southwestern Japan. The Kushikino deposit comprises fissure-filling veins within Neogene andesitic volcanics that overlie unconformably Cretaceous sedimentary basement. The veins consist of gold- and silver-bearing quartz and calcite with minor amounts of adularia, sericite and sulfides. Although carbon and oxygen isotopic data for the veins indicate a meteoric origin of the ore fluid, finite element simulations suggest that the vein system might have formed in direct response to magma intrusion. In particular, geophysical data suggest that intruding magma has uplifted the basement rocks, thereby producing fractures and veins and a positive Bouguer anomaly, and providing the heat necessary to drive an ore-forming hydrothermal system.The second component of this study has been to investigate the nature and evolution of the Kushikino and Hishikari epithermal systems. Isotope data document the geochemical evolution of the hydrothermal fluids. We conclude that the existence of sedimentary basement rocks at depth might have affected the strontium and carbon isotopic ratios of the Kushikino and Hishikari ore fluids. The 87Sr/86Sr ratios and δ13C–δ18O trend reveal that major ore veins in the Hishikari deposit can be distinguished from shallow barren veins. It was suggested isotopically that fluids responsible for the barren veins in nearby shallow and barren circulation systems were only controlled by the shallow host rocks. Such multi-isotope systematics provide a powerful tool with which to determine the center of hydrothermal activity and thereby document the evolution of hydrothermal fluids. 相似文献
12.
13.
秦岭凤太矿田层控铅锌(铜)矿床的氧化硅产出特征及其硅质来源 总被引：1，自引：0，他引：1
秦岭凤太矿田的所有铅锌(铜)矿床中都含有大量的氧化硅，前人资料中往往以沉积或蚀变单一形成方式论其成因，非此即彼。本文提出氧化硅有三种产出类型，以同生沉积型为主，其次为成岩后生阶段交代灰岩者，第三类为造山期形成的脉体。三类氧化硅的产出特征有许多不同，但硅质来源一致，即均来自深部地层和岩石中循环的含矿热液。对矿床中氧化硅的研究不仅有助于深入探讨矿床的成因，而且对于该类矿床的勘查有较重要的意义。 相似文献
14.
黔东南地处江南造山带西南段雪峰隆起西南端,区内金矿床(点)广布,是湘黔金矿集中区的重要组成部分。平秋金矿是该区金矿床的典型代表,其矿体产于下江群番召组浅变质火山-沉积岩,严格受北东向断裂褶皱控制。为理清其成因,对平秋金矿床含矿石英脉中的石英包裹体进行了氢、氧同位素测试。结果显示,其δD为-51.3‰~-59‰,δ18OH2O-SMOW为4.46‰~8.16‰,表明平秋金矿成矿期流体以变质水为主。对成矿期黄铁矿的硫同位素分析结果表明,其δ34S值为-1.86‰~4.55‰,而围岩下江群浅变质岩中黄铁矿的δ34S值为9.63‰~13.56‰,二者相差巨大,表明矿床中硫不是直接来自于赋矿围岩。根据上述氢、氧、硫同位素测定结果并结合区域地质背景,本文认为平秋金矿的成矿流体和成矿物质源自下伏地层的变质脱水作用,成矿作用与加里东运动造成的变质变形有关。 相似文献
15.
J. A. Saunders D. L. Unger G. D. Kamenov M. Fayek W. E. Hames W. C. Utterback 《Mineralium Deposita》2008,43(7):715-734
Epithermal deposits with bonanza Au–Ag veins in the northern Great Basin (NGB) are spatially and temporally associated with
Middle Miocene bimodal volcanism that was related to a mantle plume that has now migrated to the Yellowstone National Park
area. The Au–Ag deposits formed between 16.5 and 14 Ma, but exhibit different mineralogical compositions, the latter due to
the nature of the country rocks hosting the deposits. Where host rocks were primarily of meta-sedimentary or granitic origin,
adularia-rich gold mineralization formed. Where glassy rhyolitic country rocks host veins, colloidal silica textures and precious
metal–colloid aggregation textures resulted. Where basalts are the country rocks, clay-rich mineralization (with silica minerals,
adularia, and carbonate) developed. Oxygen isotope data from quartz (originally amorphous silica and gels) from super-high-grade
banded ores from the Sleeper deposit show that ore-forming solutions had δ
18O values up to 10‰ heavier than mid-Miocene meteoric water. The geochemical signature of the ores (including their Se-rich
nature) is interpreted here to reflect a mantle source for the “epithermal suite” elements (Au, Ag, Se, Te, As, Sb, Hg) and
that signature is preserved to shallow crustal levels because of the similar volatility and aqueous geochemical behavior of
the “epithermal suite” elements. A mantle source for the gold in the deposits is further supported by the Pb isotopic signature
of the gold ores. Apparently the host rocks control the mineralization style and gangue mineralogy of ores. However, all deposits
are considered to have derived precious metals and metalloids from mafic magmas related to the initial emergence of the Yellowstone
hotspot. Basalt-derived volatiles and metal(loid)s are inferred to have been absorbed by meteoric-water-dominated geothermal
systems heated by shallow rhyolitic magma chambers. Episodic discharge of volatiles and metal(loid)s from deep basaltic magmas
mixed with heated meteoric water to create precious metal ore-forming fluids. Colloidal nanoparticles of Au–Ag alloy (electrum),
naumannite (Ag2Se), silica, and adularia, likely nucleated at depth, traveled upward, and deposited where they grew large enough to aggregate
along vein walls. Silica and gold colloids have been reported in hot springs from Yellowstone National Park, suggesting that
such processes may continue to some extent to the present. However, it is possible that the initial development of the mantle
plume led to a major but short-lived “distillation” process which led to the mid-Miocene bonanza ore-forming event.
相似文献
| J. A. SaundersEmail: |
16.
四川丹巴县独狼沟金矿床是扬子陆块西缘金成矿带上的一个大型金矿床。矿体呈较高品位、较厚单体石英脉充填于构造破碎带之间,呈透镜状、似层状和层状产出,受断层构造影响极为明显,具热液矿床特征。矿物学、锆石U-Pb测年成果和稀土元素及微量元素等方面研究显示矿床主要受两期热液成矿作用影响,早期热液成矿作用形成以磁黄铁矿、黄铁矿等高温热液矿物为主的金矿体,时限限定于184.2±1.1 Ma;晚期热液成矿作用则形成以黄铜矿、叶碲铋矿等中温热液矿物为主的金矿体,时限限定于156.5±4.3 Ma。成矿流体氢氧同位素组成表明其与该时期区域岩浆作用存在一定关联而与区域变质作用关系不密切。S同位素组成反映出其来源为深部来源的属性,在Pb同位素组成的研究中也对这一观点进行了验证。成矿流体被认为是来自交代岩石圈地幔,在早侏罗世软流圈上涌事件影响下交代岩石圈地幔中挥发分上涌并活化上覆地层中的金,从而形成富金成矿流体并沿区域性深大断裂上移就位于地壳岩石地层中成矿。成矿动力学机制与区域碰撞造山后由挤压向伸展转换的大地构造背景密切关联,认为独狼沟金矿床为典型造山型金矿床。 相似文献
17.
Greg B. Arehart 《Ore Geology Reviews》1996,11(6):383-403
Sediment-hosted disseminated gold (SHDG) deposits comprise a major portion of the gold production and reserves in the US. Although presently known to be common only in western North America, SHDG deposits are a significant source of world gold production. These deposits are characterized by extremely fine-grained disseminated gold, hosted primarily by arsenian pyrite. Other metals show very little enrichment although in addition to As, anomalous concentrations of elements such as Sb, Hg, Tl and Ba are utilized as exploration tools. The host rocks are dominantly silty carbonates, but ore concentrations are also present in siliceous and silicified rocks as well as intrusive rocks. Alteration consists of decarbonatization, silicification (jasperoid formation) and argillization, which are arranged both spatially and temporally in that order. Argillic alteration is zoned from kaolinite-dominated cores to sericite-dominated margins. The deposits commonly exhibit significant structural (faults) and stratigraphic (composition/permeability) controls. Until the last few years, SHDG deposits were considered as near-surface, epithermal type deposits in origin. Because of their fine-grained nature and the lack of macroscopic features such as veins, it has proven quite difficult to extract geochemical data that are clearly related to their genesis. However, fluid inclusion data indicate pressures corresponding to depths of 2–4 km under lithostatic conditions. Temperatures are constrained by fluid inclusions and phase equilibria to near 225°C. Stable isotope data from alteration minerals and fluid inclusions indicate that the ore fluids were dominated by meteoric waters, some of which had clearly exchanged oxygen with wallrocks during their passage through the crust. Although the data vary, most ore fluids probably had δD values near −150‰ and δ18O values ranging from −10 to +5‰. Sulfur isotope values reported from SHDG deposits span a wide range, from −30 to +20‰ (sulfides) and 0 to >45‰ (sulfates). Ore-related sulfides (pyrite, realgar) fall at the upper end of the range reported for sulfides. The alteration and mineral assemblage indicate the ore fluids were probably near neutral and gold was likely carried as a bisulfide complex. The depositional mechanism(s) probably included mixing, cooling and oxidation. These mechanisms are consistent with the observed alteration features, i.e. quartz precipitation, calcite dissolution and sericite-kaolinite coexistence. It also explains the presence of both siliceous ores containing native Au and sulfide ores containing Au in pyrite. The extreme variations in sulfur isotopes as seen at Post and fluid inclusion data from Carlin may be indicative of some phase separation (‘boiling’), but such relations have not been documented in other deposits and the importance of phase separation to gold deposition appears minimal. 相似文献
18.
勐满金矿床位于云南省勐海县境内,地处临沧-景洪褶皱束之临沧-澜沧复背斜南部,截至2005年探明金矿资源量17t,主矿体属于地表红土型氧化矿,平均品位为0.60×10-6。文章基于对勐满金矿床矿区内新元古界曼来组片岩和中侏罗统花开左组碎屑岩及矿区外围东部的临沧花岗岩的LA-ICP-MS锆石U-Pb年龄测定,探讨了曼来组片岩和花开左组碎屑岩地层的物质来源,追溯母岩的物质源区,并结合矿区普遍发育的硅化岩和硅质脉体的地球化学特征,分析了金成矿的物质来源。勐满金矿床曼来组中主要碎屑锆石年龄为(957.0±9.8)Ma,属新元古代早青白口纪;中侏罗系花开左组主要碎屑锆石年龄为(224.2±2.8)Ma,与临沧花岗岩基中2件黑云母二长花岗岩的年龄(分别为(228.7±2.8)Ma和(229.4±2.0)Ma)一致,表明花开左组地层的物质来源可能与临沧花岗岩有关。微量元素测试结果显示,矿区硅化岩与硅质脉体具有相似的稀土元素配分模式与微量元素组成,均表现为富集U、Th、Pb等大离子亲石元素,亏损Zr、Hf、Nb、Ta等高场强元素,轻稀土元素明显富集,重稀土元素亏损,中-弱的Eu负异常,Ce异常不明显,与矿区围岩及临沧花岗岩体南部的黑云母花岗岩具有相似的变化趋势。硅化岩稀土元素总量为42.3×10-6~311.0×10-6,平均为131.8×10-6;硅质脉体稀土元素总量为5.0×10-6~280×10-6,平均为56.8×10-6,显示硅化岩相对于硅质脉体具有更高的稀土元素总量。硅质脉体((La/Yb)N为4.3~133.4,平均36.7)相对于硅化岩((La/Yb)N为2.1~26,平均为8.5)具有更高的轻、重稀土元素分馏特征。硅化岩的地球化学特征变化介于围岩与硅质脉之间,表明硅化岩既继承了围岩特征,又有经热泉活动改造的痕迹。综合锆石年代学结果与沉积物源分析,认为矿区花开左组砂岩主要为临沧岩体经受风化搬运沉积的产物,曼来组向花开左组提供金的量不足以形成花开左组中的碎屑岩型矿体,热泉活动产生的流体是金成矿的另一重要物质来源,同时是导致金后期富集的重要因素。据此推断,花开左组是赋矿层位,而并非矿源层。结合低硫型矿床标志性矿物冰长石的出现,提出勐满金矿属于典型的与热泉活动有关的低硫型浅成低温热液金矿。 相似文献
19.
Abstract. Intrusion‐related gold deposits are widely distributed within the North China craton or along its marginal fold belts. Presently, about 200 individual intrusion‐related gold deposits (prospects) have been discovered, among which Yuerya, Anjia‐yingzi, Linglong, Jiaojia, Chenjiazhangzi, Qiyugou, Jinjiazhuang, Dongping, Hougou, Huangtuliang, Guilaizhuang, Wulashan and Donghuofang are the most important ones. In general, the intrusion‐related gold deposits can be classified into three major groups according to their host rocks: (1) hosted by or related to felsic intrusions, including (la) calc‐alkaline granitoid intrusions and (lb) cryptoexplosion breccia pipes; (2) related to ultramafic intrusions, and (3) hosted by or related to alkaline intrusions. The first group contains the Yuerya, Anjiayingzi, Linglong, Jiaojia, Chenjiazhangzi and Qiyugou gold deposits. Gold mineralization at these deposits occurs within Mesozoic Yanshanian calc‐alkaline granitoid intrusions or cryptoexplosion breccia pipes as gold‐bearing quartz veins and replacement bodies. Pyrite, galena, sphalerite, chalcopyrite, native gold and electrum are major metallic minerals. The Jinjiazhuang deposit belongs to the second group, and occurs within Hercynian diopsidite and peridotite as quartz veins and replacement bodies. Pyrite, marcasite, arsenopyrite, native gold and electrum are identified. The third group includes the Dongping, Hougou, Huangtuliang, Guilaizhuang, Wulashan and Donghuofang deposits. Gold mineralization at these deposits occurs predominantly within the Hercynian alkaline intrusive complexes as K‐feldspar‐quartz veins and replacement bodies. Major metal minerals are pyrite, galena, chalcopyrite, tellurides, native gold and electrum. All these pyrite separates from Hercynian and Yanshanian intrusions or cryptoexplosion pipes associated with the gold deposits show a broad range in δ34S value, which is overall higher than those Precambrian rocks and their hosted gold deposits. For the alkaline intrusion‐related gold deposits, the δ34S values of the sulfides (pyrite, galena and chalcopyrite) from the deposits increase systematically from orebodies to the alkaline intrusions. All of these intrusion‐related gold deposits show relatively radiogenic lead isotopic compositions compared to mantle or lower crust curves. Most lead isotope data of sulfides from the gold ores plot in between the fields of the intrusions and Precambrian metamorphic rocks. Data are interpreted as indicative of a mixing of sulfur and lead from magma with those from Precambrian metamorphic rocks. Isotopic age data, geological and geochemical evidences suggest that the ore‐forming materials for the intrusion‐related gold deposits were generated during the emplacement of the Hercynian or Yanshanian intrusion. The calc‐alkaline or alkaline magma may provide heat, volatiles and metals for the intrusion‐related gold deposits. Evolved meteoric water, which circulated the wall rocks, was also progressively involved in the magmatic hydrothermal system, and may have dominated the ore fluids during late stage of ore‐forming processes. Therefore, the ore fluid may have resulted from the mixing of calc‐alkaline or alkaline magmatic fluids and evolved meteoric water. All these intrusion‐related gold deposits are believed to be products of Hercynian or Yanshanian calc‐alkaline and alkaline igneous processes along deep‐seated fault zones within the North China craton or along its marginal belts. 相似文献
20.
新疆托库孜巴依金矿床地质特征及成因 总被引：2，自引：0，他引：2
新疆托库孜巴依金矿床的地质、地球化学特征以及同位素年龄,氢、氧、硫等同位素测试和流体包裹体研究表明,该矿床经历了热液成矿期和地表氧化期2个成矿期,工业矿体主要富集在热液期的金-硫化物-碲化物-石英阶段。含矿石英脉中黄铁矿的δ(34S)值与围岩硫特征基本相符,具上地幔源δ(34S)分布特征。石英中包裹体氢氧同位素组成落于大气降水线之下,在变质水、岩浆水下部边缘,具混源特征。铅同位素组成落在上地幔和造山带增长线之间偏造山带侧。成矿流体气相成分以水为主,CO2、CO成分很少,液相离子成分以Ca2+,Na+,K+,HCO3-,SO24-为主。流体包裹体的盐度为6.00%～9.44%,密度为0.763～0.922g/cm3。均一温度为275～324,207～273,207～218,191～222℃。托库孜巴依金矿床属于韧性剪切带型金矿床。构造变形作用促使流体萃取了阿勒泰组上亚组第二岩性段变质火山岩或火山沉积岩中的成矿元素,导致金元素在有利的空间形成含金石英脉,后期岩浆侵入活动为金的进一步富集提供了热源和流体。 相似文献