共查询到20条相似文献，搜索用时 13 毫秒
1.
西藏冈底斯南缘雄村铜金矿床成矿斑岩厘定及其锆石U-Pb和黑云母Ar-Ar年龄分析 总被引：1，自引：0，他引：1
雄村特大型斑岩铜金矿床主要以细脉浸染状产于强烈蚀变岩石中,赋矿岩石原岩成因类型存在争议。本文对多个赋矿蚀变岩石作了系统光薄片显微鉴定,在多个蚀变较弱的矿化样品中发现赋矿岩石具斑状结构,其基质主要为钾长石,斑晶主要为斜长石、钾长石及少量石英,显示石英正长斑岩及二长斑岩(少量)矿物组成特征。结合前人工作,可以认为雄村铜金矿床赋矿岩石为正长斑岩、火山岩及少量二长斑岩。正长斑岩发育斑岩铜金矿床成矿早期常见的钾硅化蚀变及磁铁矿化蚀变,锆石具高的Ce4+/Ce3+比值(334~3084,平均值为1169),显示高氧逸度岩浆特征,和世界斑岩铜金矿床成矿岩体一致;这表明石英正长斑岩为雄村铜金矿床成矿岩体。石英正长斑岩锆石LA-ICP-MS U-Pb年龄为173.7±2.1Ma(MSWD=0.23),石英正长斑岩钾化阶段形成的黑云母40Ar/39Ar坪年龄为48.3±0.9Ma(MSWD=1.58),远小于锆石U-Pb年龄却与矿区东北部始新世花岗岩基的年龄一致,显示Ar-Ar年龄受后期地质事件影响而发生重置。通过上述研究,可以认为雄村铜金矿床为与石英正长斑岩有关的斑岩型矿床,形成时代约173Ma,和新特提斯洋洋壳向北俯冲诱发的岩浆事件有关,矿区内云母受后期地质事件影响重置,不能记录其形成时代。 相似文献
2.
巴达铜金矿位于藏东富碱斑岩带南段,是藏东地区近年来新发现的大型铜金矿。虽然对巴达铜金矿开展了大量勘查工作,但对该矿床的成因尚未取得共识。本文基于详细的野外调研、岩心与坑道编录及系统的镜下鉴定,对巴达铜金矿床地质特征进行研究。巴达矿床主要产于石英二长斑岩中,局部产于斑岩和砂岩地层的接触带内。矿床发育的围岩蚀变主要为青磐岩化、钾化、绢英岩化,高岭土化、蛋白石化、蒙脱石化次之,蚀变分带从内向外依次为钾硅酸盐化带、绢英岩化带、青磐岩化带、高岭土化带,铜金矿体主要赋存于钾硅酸盐化和绢英岩化带内,铜矿化主要以黄铜矿形式产出,金矿化主要以银金矿形式产于白云石±石英+细粒黄铁矿±黄铜矿脉中,铜矿化与金矿化呈正相关,矿体的产出受北西向逆冲断层的控制。与典型斑岩和浅成低温热液矿床不同,巴达铜金矿化主要产于白云石±石英+黄铁矿脉中;矿床内既发育碳酸盐、伊利石、绢云母和黄铁矿、黄铜矿、方铅矿、黝铜矿、低FeS闪锌矿等一套中硫型浅成低温热液矿床的蚀变矿物组合,又发育符合碱性斑岩系统的特征矿物赤铁矿。基于以上特征判断,巴达铜金矿矿床成因类型应为与富碱斑岩有关的浅成低温热液矿床,巴达铜金矿矿床成因的厘定,为下一步找矿提供了理论指导。 相似文献
3.
汉南地区晋宁晚期铜-金成矿事件的确认及意义 总被引：1，自引：0，他引：1
汉南地区位于扬子克拉通北缘西段。目前,在川、陕两省已在该区发现了数十个矿床(点)。其中,广泛分布的铜-金矿床(点)具有热液型矿化特征,成矿条件有利,具有寻找大-中型矿床的远景。为了查明这些铜-金矿产资源的形成时代,文章运用LA-ICP-MS锆石U-Pb法和单矿物~(40)Ar/~(39)Ar法对汉南地区有代表性的矿床(点)进行了成矿年代学研究。其结果显示,潘坝成矿期热液脉的锆石U-Pb年龄为(744±10)Ma,黑云母和钾长石~(40)Ar/~(39)Ar视年龄介于740 Ma~700 Ma之间。元山寺的成矿期白云母~(40)Ar/~(39)Ar坪年龄为(744±4)Ma,等时线年龄为(748±7)Ma。由于本次测试选择了成矿期矿物,其结果可以代表成矿时代。因此,汉南很可能存在晋宁晚期的铜-金成矿事件。根据区域地质演化历史,笔者认为汉南铜-金矿化(744 Ma)是造山晚期加厚岩石圈下部(山根)拆沉的结果。 相似文献
4.
多光谱遥感技术预测矿产资源的潜能——以蒙古国欧玉陶勒盖铜金矿床为例 总被引：9，自引：0，他引：9
建议把蚀变遥感异常作为一个新的找矿参数,文中讨论了蚀变遥感异常的地质基础和光谱前提。在矿床地质学和蚀变矿物光谱参数特征的基础上,编制了一张用于蚀变遥感异常提取及对其地质解释的表格。设计了从ETM+和ASTER数据中提取羟基蚀变矿物组合信息的独特流程方案。这个方案称之为"去干扰异常主分量门限化技术",文中示以简化的流程图。ETM+数据用来研究位于欧玉陶勒盖铜金矿床东北部的汉保各德中酸性火成杂岩体岩性特征,ASTER近红外和短波红外数据用来提取欧玉陶勒盖斑岩铜金矿矿床及其近区的羟基异常,通过选择性主分量分析判断欧玉陶勒盖铜金矿矿床的矿床类型为斑岩型。已知矿区各矿体的羟基异常都十分清晰,此外在矿床西部还发现了三个新的有希望的羟基异常。此工作进一步展示出多光谱遥感技术对于金属矿床的预测具有极好的潜能。 相似文献
5.
国外铁氧化物铜-金矿床的特征及其研究现状 总被引：22，自引：0，他引：22
铁氧化物铜-金矿床是一类具许多共同特征但成因联系不太密切的矿床类型，近来已成为国外铜-金勘探的主要矿床类型之一。该类矿床以矿石中含有大量的铁氧化物（磁铁矿或赤铁矿）且伴有很强的区域性钠（-钙）质蚀变为特征，可以产于元古代克拉通内或新生代大陆边缘岛弧环境，其周围具火成岩或含蒸发盐层，时空上与之有关的侵入岩为磁铁矿系列花岗岩，矿化主要产于近区域主断裂的羽状次级断裂中。部分该类矿床的形成与一定的主岩类型有关，而多数矿床可能由高盐度 H2O-CO2-盐混合流体的不混溶作用形成，且矿化通常与钾化有关。对成矿流体是主要来自岩浆还是受围岩控制尚有争论，成矿模式有蒸发盐来源模式、外来流体加热模式和岩浆-热液流体模式。但对部分该类矿床详细的流体包裹体和稳定同位素研究表明成矿流体主要源于岩浆。对该类矿床进行地球物理勘探需要考虑磁铁矿、硫化物和Cu-Au矿化之间的相互关系。在我国开展对该类矿床的研究将有益于发现新的铜资源基地。 相似文献
6.
文章通过对东准噶尔蒙西矿床蚀变、矿化和元素分带特征的研究,厘定了蚀变类型及其时空分布规律,探讨了两期矿化蚀变所对应的斑岩体,初步建立了矿床成矿模型。结果显示蒙西斑岩铜矿区蚀变与成矿具双系统叠加结构:地表和浅部的钾化和铜钼矿化与花岗斑岩密切共生。矿区大面积绢英岩化-黄铁矿化-青磐岩化、深部发育的钾化磁铁矿化,及从上往下的Ag、Pb-Zn与Au垂向分带的矿化与深部发育的闪长玢岩有关。地表和浅部花岗斑岩及其伴生的钾化、铜钼矿化是花岗斑岩铜钼矿化蚀变系统的根部与残留,而闪长玢岩成矿系统以铜金矿化为特征。基于新建立的成矿模型与已有的勘探成果,推测深部存在隐伏的Cu-Au矿体。 相似文献
7.
碱性岩相关铜-金(钼)矿床的研究进展 总被引：1，自引：0，他引：1
由于超过20%的大型-超大型铜-金(钼)矿床与碱性岩浆有关,因此,该类矿床引起矿床学家的广泛关注。碱性岩有关的铜-金矿床的成矿岩体、物化条件及围岩种类各具特色,成矿成因类型多样,主要的成因类型为斑岩型铜-金(钼)、浅成低温热液脉型金-铜(钼)。总体上,该类矿床的矿化和蚀变具有一定的特征:该类矿床多产出在伸展环境下、均富碲化物矿化、有大量的钾质交代作用、含有氟矿物质和钒云母等,成矿蚀变亦有一定的规律。长英质岩石中经常发生钾长石蚀变,而绢云母、碳酸盐和钾长石的混合蚀变常出现在中基性侵入岩中,水热合成石英和酸性蚀变十分罕见。这种特征矿化可能与碱性岩浆流体演化有关,这种流体富含CO_2,且在高氧逸度、低硫逸度条件下释放。在伸展背景下的碱性-钙碱性省寻找此类矿床具有巨大的勘查潜力,尤其在碱性岩体中心及其外围可能形成勘探的靶区。在中国与碱性岩有关的金矿床亦有广阔的找矿前景,在借鉴国外寻找此类矿床经验的同时,仍需加强对与矿化作用有关的岩浆体活动的研究。 相似文献
8.
鄂东南矿集区典型矽卡岩-斑岩矿床蚀变矿物短波红外(SWIR)光谱研究与勘查应用 总被引：6，自引：0，他引：6
鄂东南矿集区是我国著名的矽卡岩-斑岩型铜铁金矿床产区,研究程度较高,近年来矿产勘查进入了深部找矿的新阶段,需要较新的勘查方法与思路。本文介绍了利用短红外光谱(SWIR)技术,对鄂东南典型的铜绿山矽卡岩型Fe-Cu-Au矿床、鸡冠嘴矽卡岩型Cu-Au矿床、铜山口矽卡岩-斑岩型Cu-Mo-W矿床进行的蚀变矿物综合研究最新成果。在确定蚀变矿物组合类型、形成期次、蚀变分带的基础上,揭示了主要蚀变矿物SWIR特征值的指示规律,并进一步提取各个矿床的蚀变矿物SWIR勘查标志,如铜绿山矿床富Fe绿泥石(Pos2250 2253nm)、高结晶度高岭石族(Pos2170 2170nm,Dep2170 0. 18)、白云母族-蒙脱石异常Pos2200值( 2212nm或2202nm)、高岭石、迪开石及皂石的大量出现,可以作为铜绿山铜铁金矿床有效的蚀变矿物勘查标志;鸡冠嘴矿床白云母族-蒙脱石Pos2200特征值的高值( 2209nm)区域对矿体位置具有较好的指示性;铜山口矿床绿泥石的高Fe-OH吸收峰位值(Pos2250 2249nm)和高Mg-OH吸收峰位值(Pos2335 2333nm)的高频出现,可以作为铜山口铜钼钨矿床的有效勘查标志。这些研究成果表明蚀变矿物可以为鄂东南矿集区提供有效的勘查标志体系,同时,这些最新的勘查标志也在铜绿山铜铁金矿床得到了初步的应用和验证。 相似文献
9.
Fareeduddin I. R. Kirmani Suresh Chander 《Journal of the Geological Society of India》2012,80(1):5-38
The Salumber-Ghatol belt in Rajasthan, India, situated along southern margin of the Aravalli Craton, hosts a cluster of Cu-Au deposits in calcitic and dolomitic marbles that belong to Debari Group of the Paleo-mesoproterozoic Aravalli Supergroup. The Fe-Mn rich dolomitic marble of the Delwara Formation hosts Cu-Au-Fe-oxide mineralization at Ghagri and associated distal K-Fe-Mg rich altered rocks (cryptocrystalline microcline + magnesioriebeckite + magnetite + phlogopite) and proximal feldspathised carbonate rocks (medium grained albite + microcline + dolomite + magnetite). The calcitic marble of Mukandpura Formation hosts Dugocha Cu-Au deposit with development of distal graphitetourmaline-bearing albitites and proximal albite-microcline-magnetite rocks. Calcite and dolomite carbonates of Bhukia region with development of albite-actinolite-bearing alteration assemblages host the largest of the Cu-Au deposits in this belt. The second generation folds and associated ductile-brittle shear zones of the multiply deformed events constitute conduits for the mineralizing fluids at all locations in this belt. 相似文献
10.
A new Cu-Au alloy occurrence is located at the southeastern flank of the Malye Kopty massif of ultramafic rocks in the Vendian-Early
Cambrian Kaa-Khem ophiolitic belt. Lithic clasts with Cu-Au alloy segregations (up to 15 mm in size) intergrown with other
minerals were found in alluvium of the Kara-Oss Creek valley, which extends along the fault zone crosscutting ultramafic rocks.
Cu-Au alloy occupies the main volume of clasts and fills the network of veinlets in grained aggregates consisting of andradite
(2–18% grossular component) and diopside (X
Fe = 0.01–0.05). Cu-Au alloy contains small ingrowths of andradite (up to 43% grossular component), diopside (X
Fe = 0.14–0.19), chlorite (penninite), chalcocite that contains up to 1.5 wt % Au, Cu-bearing greenockite (6.07–13.67 wt % Cu,
0.48–1.56 wt % Zn, and 0.76–1.06 wt % Au), and magnetite. The chemical composition of Cu-Au alloy is nonuniform. The central
parts of large Cu-Au alloy segregations consist of Ag-bearing tetraauricupride (AuCu) blocks (3.2–6.4 wt % Ag). They contain
veinlet-shaped AuCu zones with 13.3–14.5 wt % Ag. The AuCu blocks are cemented by late Cu-Au alloy, whose composition is close
to auricupride (AuCu3). Taking into account the limits of component miscibility in the Au-Ag-Cu system, the temperature of the Cu-Au alloy formation
was estimated at 350–600°C. This temperature corresponds to the formation conditions of garnet-pyroxene rodingite mineral
assemblage (Plyusnina et al., 1993). The studied Cu-Au alloy samples from the Malye Kopty massif are very similar to Cu-Au
alloy minerals hosted in the Alpine-type ultramafic rocks of the Karabash massif in the southern Urals. This similarity is
confirmed by identical chemical compositions of pyroxene, garnet, and chlorite, and similar PT conditions of their formation. The data show that primary ore mineralization of gold-rodingite type occurs in the Kaa-Khem
ophiolitic belt. 相似文献
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西藏波龙斑岩铜金矿床的Re-Os同位素年龄及其地质意义 总被引：28，自引：5，他引：23
波龙斑岩铜金矿紧邻多不杂矿床,是多龙矿集区内新发现的一个超大型矿床。波龙矿床早期有两次成矿花岗闪长斑岩侵位,随后较晚期花岗斑岩侵位;地表广泛分布绢英岩化蚀变,深部发育钾化。本文对采于波龙斑岩型铜金矿床内石英-辉钼矿脉中的4件辉钼矿样品进行了Re-Os同位素测试,获得等时线年龄为119.4±1.3Ma (MSWD=0.63, n=4)。此年龄代表了波龙矿床的成矿年龄,与多不杂斑岩型铜金矿床的成矿年龄一致。波龙和多不杂斑岩型铜金矿床紧邻,并具有一致的成矿年龄,可能表明两个矿床的成矿受控于相同的构造-岩浆-成矿事件;斑岩铜矿具有成群分布的特征,波龙和多不杂斑岩铜金矿床的发现也暗示多龙矿集区具有找到其他大型斑岩铜金矿的潜力。 相似文献
14.
十二排钼矿床位于上杭-云霄断裂带与闽西南拗陷的复合部位,是紫金山铜金矿田外围新近探明的一处具有中大型远景的斑岩型钼矿床。野外地质调查显示,其钼矿化呈细脉状、网脉状主要产出于黑云母二长花岗岩和黑云母花岗斑岩中。热液蚀变具有斑岩型矿床的分带特征,由黑云母花岗斑岩向外依次发育钾硅酸盐化带、绢英岩化带和青磐岩化带,钼矿体主要赋存于绢英岩化与钾硅酸盐化构成的叠加带中。锆石U-Pb定年结果表明,黑云母二长花岗岩和黑云母花岗斑岩分别形成于(143.1±0.9)Ma和(143.5±0.4)Ma。4件辉钼矿样品的Re-Os加权平均年龄为(143.9±2.1)Ma。辉钼矿的w(Re)为1.2×10~(-6)～7.8×10~(-6),说明成矿物质可能主要来自地壳。岩石地球化学分析结果显示,十二排含矿花岗岩具有相似的主量和微量元素组成,均属于弱过铝质高钾钙碱性I型花岗岩,其中,黑云母花岗斑岩表现出高分异花岗岩特征,两者可能是古老变质基底来源的熔体经历不同程度分异结晶的产物,并混入有少量幔源物质。综合已有的资料,文章认为十二排斑岩型钼矿化与早白垩世早期花岗质岩浆活动密切相关,上杭-云霄断裂带存在古太平洋板块俯冲后撤引发构造体制转换阶段的成岩成矿响应,进一步找矿勘查工作应加强评价早白垩世早期高分异花岗岩体的钼多金属成矿潜力。 相似文献
15.
Weiqiang Li Simon E. Jackson Norman J. Pearson 《Geochimica et cosmochimica acta》2010,74(14):4078-239
Significant, systematic Cu isotopic variations have been found in the Northparkes porphyry Cu-Au deposit, NSW, Australia, which is an orthomagmatic porphyry Cu deposit. Copper isotope ratios have been measured in sulfide minerals (chalcopyrite and bornite) by both solution and laser ablation multi-collector inductively coupled plasma-mass spectrometry (MC-ICP-MS). The results from both methods show a variation in δ65Cu of hypogene sulfide minerals of greater than 1‰ (relative to NIST976). Significantly, the results from four drill holes through two separate ore bodies show strikingly similar patterns of Cu isotope variation. The patterns are characterized by a sharp down-hole decrease from up to 0.8‰ (0.29 ± 0.56‰, 1σ, n = 20) in the low-grade peripheral alteration zones (phyllic-propylitic alteration zone) to a low of ∼−0.4‰ (−0.25 ± 0.36‰, 1σ, n = 30) at the margins of the most mineralized zones (Cu grade >1 wt%). In the high-grade cores of the systems, the compositions are more consistent at around 0.2‰ (0.19 ± 0.14‰, 1σ, n = 40). The Cu isotopic zonation may be explained by isotope fractionation of Cu between vapor, solution and sulfides at high temperature, during boiling and sulfide precipitation processes. Sulfur isotopes also show an isotopically light shell at the margins of the high-grade ore zones, but these are displaced from the low δ65Cu shells, such that there is no correlation between the Cu and S isotope signatures. Fe isotope data do not show any discernable variation along the drill core. This work demonstrates that Cu isotopes show a large response to high-temperature porphyry mineralizing processes, and that they may act as a vector to buried mineralization. 相似文献
16.
《Chemie der Erde / Geochemistry》2021,81(4):125822
The Dongguashan Cu-Au deposit located in the eastern portion of the Tongling mining district, the Lower Yangtze River Metallogenic Belt (LYRB), Eastern China is a typical one associated with the Qingshanjiao quartz monzodiorite, including porphyry, skarn, and stratabound ores. In order to constrain the petrogenesis of the intrusive rocks and associated Cu-Au mineralization, detailed analyses of the zircon geochronology and geochemistry, whole-rock geochemistry and Sr-Nd-Pb isotopes, and zircon Lu-Hf isotopes were performed. Magmatic zircons from quartz monzodiorite yield U-Pb ages of 136–138 Ma, revealing their formation ages of early Cretaceous. Geochemical characteristics of the quartz monzodiorites (SiO2 = 63.6–66.2 wt%, high Sr, low Y and Yb concentrations) discriminate their adakitic affinity. They are enriched in LILE and LREE, depleted in HFSE and HREE, and has no or slightly negative Eu anomalies. These geochemical characteristics indicate that the monzodiorites may be primarily derived from the magma mixing of mantle- and LCC-derived melts. The relatively low εNd(t) values (−11.7 to −10.7) and high (87Sr/86Sr)i ratios (0.7075 to 0.7078) may be plausibly interpreted by contamination of enriched mantle materials and/or continental crust. The high radiogenic Pb isotopes with (206Pb/204Pb)i = 17.98–18.09, (207Pb/204Pb)i = 15.51–15.53, and (208Pb/204Pb)i = 38.18–38.26 plot in the field of MORB, near the intersection of EM-1 and EM-2, and are considerably different from those of the upper and lower continental crust and the Dabie adakites, which exclude major contamination from the continental crust. Ti-in-zircon temperatures and calculated Ce4+/Ce3+ values fall within the field between MH and FMQ. The results indicate that the intrusive rocks and associated large-scale Cu-Au mineralization in the Dongguashan deposit are resulted from the magma mixing of mantle- and LCC-derived melts. in a lower magma temperature, yet higher fO2 and water content environment. 相似文献
17.
西藏多龙矿集区典型矿床(点)矿化特征与成矿作用对比研究 总被引：3，自引：2，他引：1
西藏多龙矿集区是近年来中国新发现的具有世界级潜力的铜金矿集区。该矿集区现已查明多不杂、波龙、拿若和铁格隆南4个大型-超大型矿床,并新发现地堡那木岗和拿顿矿点。文章对上述矿床(点)脉体、蚀变、矿化和流体特征开展了系统研究和对比。结果表明,多不杂、波龙和拿若矿床矿化类型以斑岩型为主,同时钾硅酸盐化、绢英岩化、青磐岩化等蚀变广泛发育,而铁格隆南矿床除上述蚀变类型外,还叠加有高级泥化蚀变,并发育与之相关的浅成低温热液型矿化。根据脉体特征对比和流体包裹体温压计算推测,上述4个矿床矿化类型的差异可能由剥蚀深度的差异所引起(前三者剥蚀深度约为2～3 km,后者约为1～1.5 km)。此外,地堡那木岗矿点蚀变类型以绢英岩化、泥化为主,该矿点发育与斑岩型金矿中类似的深色条带状石英脉,指示该地区可能存在斑岩型金矿。拿顿矿点为典型的高硫型浅成低温热液型矿化,铜金矿体赋存于角砾岩筒中。野外地质调查表明,上述矿点地表蚀变岩盖(Lithocaps)发育,并且蚀变岩盖空间分布位置与下伏铜金矿体表现出良好的匹配关系,可有效地指导找矿勘查工作。流体包裹体实验进一步表明,铜金元素在斑岩型矿化中的沉淀可能与温度降低和氧逸度的变化有关,而在浅成低温热液型矿化中的沉淀则受控于温度的降低和流体的不混溶作用。最后,在前人年代学研究基础上,结合本次实验结果构建了该地区与成矿作用有关的时空演化模型。 相似文献
18.
Adakites are commonly associated with porphyry Cu-Au ore deposits worldwide. Two groups of early Cretaceous adakites occur widely in central-eastern China but their association with mineralization contrasts sharply: adakites from the Lower Yangtze River Belt (LYRB) host one of the largest porphyry Cu-Au deposit belts in China, whereas those from the South Tan-Lu Fault (STLF), which is adjacent to the LYRB, are all ore-barren. These adakites, thus, provide a rare opportunity to explore the main factor that controls the genetic links between adakites and Cu-Au mineralization. Here we report new chronological, elemental and Sr-Nd-Pb isotopic data and present a comprehensive geochemical comparison for these two groups of adakites. At a given SiO2, the STLF adakites show lower Al2O3 and higher K2O, K2O/Na2O, MgO, Cr, Ni and Mg# than the LYRB adakites. These systematic differences may indicate a dry basaltic source for the STLF adakites and a water-enriched basaltic source for the LYRB adakites. The STLF adakites have high Sr/Y and (La/Yb)N, which are positively correlated, and low Sr/La and Ce/Pb, while the LYRB adakites show lower (La/Yb)N but higher Sr/Y, Sr/La and Ce/Pb than the STLF adakites. Furthermore, the LYRB adakites are characterized by highly radiogenic Pb isotopic compositions with 206Pb/204Pb(t) up to 18.8, which are clearly distinct from the STLF adakites with low radiogenic Pb (206Pb/204Pb(t) = 15.8-16.4). Although the high Mg# of the two groups of adakites suggest reaction with mantle peridotites during magma ascent, the geochemical comparisons indicate that the STLF adakites were derived from partial melting of the delaminated eclogitic lower continental crust, while the LYRB adakites were derived from partial melting of the seawater-altered oceanic crust that was being subducted towards the LYRB during the early Cretaceous. The petrogenetic contrasts between these two groups of high-Mg adakites, therefore, indicate that the large-scale Cu-Au mineralization is associated with oceanic slab melting, not delamination or recycling of the ancient lower continental crust, as previously proposed. 相似文献
19.
山西五台县北约15 km的白云村一带出露有叶蜡石矿及金矿化点,其形成特点与关系对区域深部找矿具有重要启示意义。该叶蜡石矿体产于经历古元古代绿片岩相变质的新太古代酸性火山岩之中(绢英片岩),切割区域片理并被晚期的辉绿玢岩截切。矿体总体呈透镜状产出,倾向北西,近东-西向延伸大于5 km,最厚处约1 km,未见底。该叶蜡石矿形成于中生代早白垩世。矿石矿物以叶蜡石和石英为主,含少量绢云母、伊利石、硬水铝石和赤铁矿等,反映出蚀变流体酸性及氧化的特征。叶蜡石矿体外围发育黄铁绢英岩化带,强度由近及远逐渐减弱。在靠近叶蜡石矿的黄铁绢英岩中,硫化物颗粒边缘常见赤铁矿化现象,应与叶蜡石化流体叠加有关。以上蚀变特征与叶蜡石化细脉灌入黄铁绢英岩相吻合。叶蜡石矿体上盘的黄铁绢英岩化带宽约0.4 km,其内发育一小型石英脉型金矿(岭底金矿),下盘的黄铁绢英岩化带最宽约1.5 km,局部发育金矿化现象((1~18)×10-6)。黄铁绢英岩中硫化物以黄铁矿为主,可见少量黄铜矿、斑铜矿和辉铜矿。金矿化黄铁绢英岩以发育大量浸染型黄铁矿为特征,该类黄铁矿无韧性变形,未见其他共生硫化物,SEM-EDS分析结果显示其内发育有明显的不可见金。黄铁绢英岩化可依据矿物变形与否分为两期。早期的蚀变分布局限,见于新太古代糜棱岩化奥长花岗岩与酸性火山岩(绢英片岩)接触带,其中的黄铁矿、绢云母和石英等矿物发育韧性变形特征;晚期的蚀变带内硫化物、绢云母和石英均无韧性变形特征。依据样品的岩相学及全岩Au、As含量特征,可以确认金矿化与晚期黄铁绢英岩化有关,与早期蚀变无关。叶蜡石矿石的H-O同位素组成(δ18OV-SMOW=11.2‰~13.9‰;δDV-SMOW=-34‰~-20‰)显示流体以气相为主,且缺乏大气水的混合。上述特征说明白云叶蜡石矿是深部岩浆侵位固结后出溶的以气相为主的热液与浅部新太古代变质火山岩反应的结果,类似于斑岩成矿系统中普遍发育的高级泥化带(岩帽)的底部蚀变特征。 相似文献
20.
西秦岭谢坑矽卡岩型铜金矿床地质特征与矿区岩浆岩年代学研究 总被引：5，自引：5，他引：0
谢坑铜金矿床位于西秦岭造山带西段,区域内主要出露下二叠统大关山群和下三叠统隆务河群,构造和岩浆活动发育.岩石学研究表明,谢坑铜金矿区内出露侵入岩主要为辉长闪长岩和辉长岩,它们是岗察岩体的重要组成部分.在辉长闪长岩与二叠纪灰岩接触带部位发育铜金和铁矿化并形成相关工业矿体.矿石类型主要有块状、脉状和浸染状三类.磁铁矿、磁黄铁矿表现为块状,黄铜矿为脉状和浸染状;脉状和浸染状黄铜矿穿插于块状磁铁矿矿石现象十分普遍,含金碳酸盐石英脉主要沿着矿石裂隙发育.围岩蚀变呈现清晰的蚀变分带现象,自岩体向外依次表现为钾化、青磐岩化和矽卡岩化.其中矽卡岩化主要发育于辉长闪长岩与灰岩接触带部位,与成矿关系密切,磁铁矿矿化主要发育于晚期矽卡岩阶段,磁黄铁矿、黄铁矿、黄铜矿等金属硫化物以及毒砂等矿物主要形成于早期硫化物阶段,金矿化主要发育于石英硫化物阶段.LA-ICP-MS锆石U-Pb测年结果表明,辉长闪长岩和角闪安山岩分别形成于243.8±1.0Ma和242.1±1.2Ma.该成岩、成矿时代与区城构造岩浆、成矿事件相一致.这些结果表明,谢坑铜金矿床为与西秦岭中三叠世孤岩浆作用密切相关的矽卡岩型矿床. 相似文献