共查询到20条相似文献，搜索用时 46 毫秒
1.
R.K. Srivastava 《Chemical Geology》1979,27(3):255-263
Igneous rocks, silicate minerals and native sulphur have been analysed for their mercury content by a microwave-excited argon plasma. Basic and ultrabasic igneous rocks have abundances between 3 and 31 ppb Hg. The granitic rocks show much larger variations. The content in the silicate minerals is highly variable, ranging from less than 1 ppb Hg in an igneous biotite to 55 ppb Hg in a pegmatitic biotite. The analysed clay minerals give 110 and 200 ppb Hg. Volcanic elemental S contain from 11 to 9300 ppb Hg, the values on the lower side being from oceanic volcanoes and on the higher side for continental or marginal volcanoes. 相似文献
2.
华北地台花岗岩和地层中金含量与金成矿的关系 总被引：10，自引：0，他引：10
华北地台的热液金矿床经常产于绿岩带中的花风岩内外接触带和变质岩中,因而许多人认为花岗岩和地层就是金矿床的矿源层和矿源岩。显然,他们瓣假设是建筑在这些岩石金的含量高于地壳、上地壳和区域背景含量上的,这样,这些花岗岩和地层可提供足够的金来形成金矿床,因而,这些地层和花岗夺被称为矿源层或矿源岩。随着金定量分析方法的改进和精度的提高 0.1×10^-9,大量测试资料表明,绿岩带中的变质岩和地层中金的丰度常较低,平均1.06×10^-9～2.3×10^-9,而与金矿有关的花岗岩金的含量更低,平均为0.6×10^-9～1．4×10^-9。并且随着花岗岩化和混合岩化程度增加而降低。因此,矿源层和矿源岩并不是前人所认为的那样,花岗岩形成过程和早期深部的成矿流体的碱交代作用过程是促使金活化转移的重要机制,也是形成金矿的主导因素。 相似文献
3.
Gold mineralization in Archaean granite-greenstone environments, especially gold-quartz veins, contributes considerably to the world's gold production. The formation of epigenetic gold mineralization in greenstone belts is generally explained by the metamorphic secretion theory. This theory is based on the assumption that the source of the gold may be komatiitic or tholeiitic lavas, pyritic chemical or clastic sediments and even granitic rocks from which, as a result of regional metamorphic overprinting, gold was extracted and concentrated in suitable structures.It has been shown that in proposed potential source rocks, gold is predominantly associated with sulfide minerals and thus relatively easily accessible to secretion and reconstitution processes.A large number of various rock types originating from granite-greenstone terranes of the Kaapvaal and the Rhodesian cratons were geochemically investigated, and the following ranges for gold determined:volcanic rocks (komatiitic and tholeiitic): 0.1–372 ppbgranitic rocks of the basement: 0.3–7.8 ppbiron-rich chemical sediments: 1.0–667 ppbStatistical treatment of the data reveals that volcanic rocks as well as iron-rich chemical sediments are favorable sources for epigenetic gold mineralization formed by metamorphic secretion, while the granitic rocks make less suitable primary gold sources. This finding explains the close spatial relationship which is common between gold-quartz veins and greenstone belts. The conspicuous abundance of epigenetic gold mineralization in the Archaean, however, is attributed to the unique geologic and metamorphic history of the granite-greenstone terranes. 相似文献
4.
金厂峪金矿有关岩石金丰度的研究 总被引：1，自引：0，他引：1
金丰度对矿床形成的意义是值得深入研究的课题。世界上多数金矿与变质岩有关,但在事实上,后者的金丰度并不是很高。金厂峪矿区变质岩金丰度亦较低,作为金矿围岩的斜长角闪岩中的金仅为3.1ppb,但是金的“易溶性”是所有与金矿有关岩石中最好的。这就使它易于在适当的成矿条件下活化、迁移和富集成矿。因此,斜长角闪岩应是金矿的最佳矿源层。 相似文献
5.
东天山石炭纪—二叠纪花岗质侵入岩的地球化学及地质意义 总被引：1，自引：0，他引：1
东天山吐哈盆地南缘至喀拉塔格—星星峡地块,晚古生代花岗质侵入岩岩石类型主要有花岗闪长岩、二长花岗岩、石英闪长岩、石英二长闪长岩。岩石地球化学特征表明：Si O2质量分数为57.3%~77.76%,全碱（K2O＋Na2O）质量分数为4.14%~10.49%,Ca O质量分数为0.49%~6.56%,Al2O3质量分数为11.39%~14.76%,铝饱和指数（A/CNK）为0.77~1.04,属于高钾钙碱性系列—钾玄质系列的准铝质花岗岩。稀土总量较高且轻稀土富集,富集Rb、Th、U、K、Pb,而亏损Nb、Ta、Ti、P,无明显负Eu异常。区域构造背景、岩石学和地球化学特征综合分析显示,东天山石炭纪—二叠纪花岗质侵入岩,是后碰撞构造演化阶段岩浆活动的产物,主要由幔源岩浆底侵引起的地壳物质部分熔融所形成的钙碱性花岗闪长质岩浆经高度演化及分异结晶作用而成。 相似文献
6.
S. N. Ahmad 《Mineralium Deposita》1977,12(1):1-21
In order to test a hypothesis on the origin of copper in the Cornwall district, 270 samples of mafic rocks, 88 samples of sedimentary rocks and 78 samples of granitic rocks have been analysed for their copper contents. Among the mafic rocks, the intrusive microgabbro has a higher mean copper content (59±32 PPM) than the spilitic pillow lavas (43±27 PPM). The abundance of copper in the sedimentary rocks appears to be related to their lithological characters. The average copper content of the grey slates with carbonaceous material (47±16 PPM) is higher than that for the noncarbonaceous grey slates (29±20 PPM) The distribution of copper in the granitic rocks shows a marked relationship with the degree of mineralisation in the region. The average copper content of the granitic rocks from the intensely mineralized region is 73±18 PPM while the granitic rocks from the less mineralized region contain an average of 21±9 PPM copper. Further, it appears that there has been a general enrichment of copper from early granitic stage to the late pegmatites. These geochemical features can be of potential use in selecting intrusive bodies for detailed exploration. The high copper content in the country rock and in the mineralized intrusion plus a likelihood of assimilation of crust in forming granitic magmas suggest that the copper deposited as hydrothermal lodes may have been derived from the country rocks of the region.The work was completed at the Department of Geology, University of Birmingham, Birmingham 15, England. 相似文献
7.
三论花岗岩按照Sr-Yb的分类:应用 总被引：12，自引：7，他引：5
在"再论"中我们提出了花岗岩按照Sr-Yb分类的新标志(张旗等,2010a),本文进一步讨论该分类的应用。文中举了国内外许多实例(包括柴达木、北祁连、内蒙古、松潘-甘孜、大别、太行、华北古元古代和华南新元古代以及土耳其、俄罗斯、巴西、刚果、波西米亚、意大利等),着重讨论了花岗岩Sr和Yb含量与其形成压力和深度的关系,指出本分类最重要的地球动力学意义在于与其形成的深度有关,并在一定条件下与其产出地区的地壳厚度有关。例如应用本方法分析华北克拉通古元古代花岗岩,很难得出该带在古元古代发生过碰撞的结论,华北克拉通是否分为东西两块也需要重新认识。又如对华南新元古代花岗岩的分析表明,华南地块内部在新元古代时地壳较薄,但是,与Rodinia大陆的裂解似乎无关。文中还对花岗岩与成矿的关系进行了讨论,提出成矿与压力有关的概念。如金铜与地壳厚度大的埃达克型和喜马拉雅型花岗岩有关,钨锡与地壳厚度薄的南岭型花岗岩有关,而不论矿床是什么类型的,只要它们与花岗岩有关,必定受矿液源区深度的控制,要么是在加厚地壳的地球动力学背景下,要么是在地壳减薄的地球动力学背景下。花岗岩无比复杂,我们用Sr和Yb两个元素对花岗岩重新进行了分类,只是一个探索性的尝试,问题肯定不少,需要广泛的实践的检验,需要深入的实验研究的检验,需要理论的探讨,需要经过一系列否定-肯定-否定的过程,才能逐渐臻于完善。 相似文献
8.
玲珑花岗质杂岩体形成的物理化学条件及其地质意义 总被引：10，自引：0，他引：10
胶东西北部是我国金矿的重要产区,招掖金矿带的形成与玲珑花岗质杂岩有密切的成因联系。玲珑花岗质杂岩是一个多期次形成的复式岩体,最终定位于燕山期。它主要由云山、崔召、玲珑片麻状花岗岩、郭家店（型）、郭家岭（型）岩体组成。本文研究了上述诸岩体形成的Ｔ、ｐ、ｆＯ２、ｆＨ２、ｐＨ２Ｏ条件及熔浆中的含水量。通过玲珑花岗质杂岩形成的物理化学条件研究得出：玲珑花岗质杂岩即不是区域变质作用中混合岩化的产物,也不是幔源岩浆分异、冷凝的产物,而是由太古宙、元古宙变质岩重熔交代所形成的原地半原地型花岗质杂岩体。玲珑花岗质杂岩,尤其是郭家岭型花岗岩对本区金矿的形成具有重要意义。重熔岩浆作用,热驱动下流体循环和含矿热液中水的浓缩（收缩）,是胶东金矿得以形成的主要原因。 相似文献
9.
本文概述了新泰地区绿岩带的基本特征,构造及其演化规律,提出花岗质岩石是由幔源物质上侵及绿岩带部分重熔形成的。文中用测得κ系数0.37,作为对比太古宙绿岩带中科马提岩的标准,并得出金在科马提岩中初始丰度值,其西带为5.99ppb,东带为2.37ppb,反映了太古宙期间本地区地幔含金的不均一性。运用算术、几何平均法,对绿岩带各岩石类型、地层单元、花岗质岩石及其岩脉的含金性统计结果表明有的岩石变异系数增大,有利于金的分散与集中。文中对金矿化带地质地球化学特征及其成晕机制进行了论述,确定了矿化带的地表与金呈明显正相关元素为Ag、As、Sb、Ph、Zn,负相关元素为Cu、Hg,矿化带的深部与金呈正相关的元素为Sb,而Ag、As、Hg、Cn、Pb、Zn则与金的相关系数趋于零。从而对区内绿岩带金矿成因进行探讨,提出了变质-岩浆-热液充填交代成矿模式,并初步提出找矿地段。 相似文献
10.
E. G. Imeokparia 《Journal of Geochemical Exploration》1982,17(2):93-108
Geochemcial distribution of tungsten in the granitic rocks of Afu Younger Granite Complex of Central Nigeria, indicates that the average tungsten content (168 ppm) of the rocks is significantly higher than any reported average abundance for granitic rocks. However, significant contrast between the rock phases is obtained only in the Igo biotite granite which is directly connected with tungsten lode mineralization.The close spatial relationship between tungsten mineralization and the Igo biotite granite suggests that the ore forming fluids were probably derived from the residual fraction of the granitic magma. Greisenization is intimately associated with mineralization and it is suggested that they both had a common process of formation. 相似文献
11.
小秦岭文峪和娘娘山花岗岩体锆石SHRIMP U-Pb年龄及其意义 总被引：13，自引：0，他引：13
对小秦岭文峪和娘娘山花岗岩体进行的锆石SHRIMP U-Pb定年和岩石地球化学分析结果表明,文峪和娘娘山黑云母二长花岗岩体属于Ⅰ型花岗岩,是太古宙太华群高级变质岩系经部分熔融的产物。它们的成岩年龄分别为138.4±2.5 Ma和141.7±2.5 Ma,略早于本区拆离伸展活动的时限,暗示了中下地壳部分熔融形成的岩浆热穹窿和花岗质岩浆在上地壳的大面积侵位导致了小秦岭变质核杂岩的发育。花岗岩体的成岩年龄都早于本区金矿床的主期成矿时代,从时间上表明了花岗质岩浆活动与金矿成矿作用无直接关系。 相似文献
12.
Many Archaean mesothermal gold deposits are spatially associated with felsic to lamprophyric minor intrusions and it has been suggested that magmatic processes related to such intrusions may be important in the genesis of these deposits. A comparison of the Pb-isotopic signature of gold-related galenas from Kambalda and Norseman with that of spatially associated minor intrusions (at the time of mineralization) indicates that the ore-fluid Pb cannot have been derived solely from the intrusions or their source regions. For both study areas, the galena Pb-isotopic compositions are bracketed by those of local volcanic (mafic) and intrusive (largely felsic) rock types. This is consistent with the ore fluid having derived metallic components from the crust (or crustally derived granitic rocks) and the mantle (or mantle-derived rocks of the greenstone succession) via metamorphic dewatering or mantle/crustal degassing. Interaction of granite-derived magmatic fluids with greenstone lithologies could plausibly produce a similar array of Pb-isotopic signatures. The Norseman data, as a whole, are more radiogenic than the Kambalda data for broadly synchronous mineralization, reflecting the greater abundance of older granitic rocks with respect to mafic/ultramafic rocks in the Norseman district. The provinciality exhibited by the Pb-isotopic composition of the ore fluid indicates that the gold-mineralizing process formed galena whose Pb-isotopic composition was very sensitive to local variations in crustal Pb-isotopic composition, either within the source region of the fluid or along fluid conduits. 相似文献
13.
Geology of the Gasa Island (Gasado), Korea, consists mainly of tuffaceous rocks, rhyolite and andesitic rocks related to Cretaceous volcanic activity. These rocks are hydrothermally altered, and are classified into the following four alteration zones based on the alteration mineral assemblages: advanced argillic alteration (alunite‐pyrophyllite‐kaolinite‐pyrite); sericitic alteration (sericite‐kaolinite‐quartz); propylitic alteration (quartz‐chlorite‐carbonate‐pyrite); and silicified zones. Alunite in the advanced argillic zone occurred in two types; a massive or disseminated type and a vein type. Most of the massive or disseminated alunites are ≥50 μm in size, whereas the size of vein alunites is <20–30 μm. Alunite grain size is greater in the central part of disseminated or massive alunite, while it is smaller toward the margins. The gold content of each alteration zone is 21–2900 ppb, 15–88 ppb, 57–1730 ppb, and 2–231 ppb, respectively. The gold content of quartz veins developed in the alteration zones is 39–715 ppb. Gold is enriched in the minerals and rocks around faults and fissures, and is strongly concentrated in the advanced argillic alteration zone around faults. Hydrothermal solutions traveling along the fracture systems might be responsible for the comparatively high gold content in the study area. δ34S of alunites occurring in the advanced argillic alteration zone range from +16.5 to +3.9‰, although most are in a comparatively narrow range from +8.6 to +5.2‰. There is no difference between disseminated or massive and vein alunites. The δ34S of pyrites in the advanced argillic alteration zone are from +4.8 to ?2.9‰. Oxygen and hydrogen isotope values of alunites are from +8.5 to 0‰ and from ?59.6 to ?97.3‰, respectively. With an assumed temperature of 200°C, δD and δ18O of hydrothermal solutions calculated for alunites are from ?53.6 to ?91.3‰, and from ?2.4 to ?8.1 for massive or disseminated alunites and from ?6.6 to ?10.9‰ for vein alunites, respectively. These data suggest that meteoric water dominated during the alunite formation. Isotopic data, geological setting, mineralogy, size of alunite and pure alunite composition (K end member) indicate that alunites of the study area were formed in the steam‐heated environment of acid sulfate alteration. 相似文献
14.
华北克拉通绿岩带型金成矿系统初析 总被引：5，自引：0，他引：5
华北克拉通中绿岩带型金矿床是我国重要的矿床类型之一，也是我国黄金产量和储量的主要来源。从构造动力体制来看，华北克拉通在漫长的演化历史中曾经达过中晚元古代的离散型陆缘，早古生代到晚古生代的汇聚型陆缘和显生宙中生代克拉通活化多个构造阶段。金矿床主要形成于克拉通活化阶段，其总的构造背景可概括为由挤压，碰撞作用晚期或期后向伸展构造的转变时期。金成矿具有明显的区域地球化学背景。虽然华北克拉通绿岩带型金矿床形成时代不尽相同，但具有相似的地质地球化学特征，并与显生宙花岗岩类侵入体具晚于花岗岩，指示金矿化是构造－花岗岩浆演化晚期的产物。因此，这些金矿床基本上可归为一个成矿系统，即绿岩带中与花岗质岩浆作用于有关的热液成矿系统。 相似文献
15.
We report quantitative X-ray diffraction, whole-rock geochemical and Sm–Nd isotope data for metabasalts from the Aspiring and Torlesse Terranes in the South Island of New Zealand. These rocks underlie the Mesozoic metasedimentary Otago Schist which is anomalously enriched in gold and host to at least one world-class orogenic gold deposit at Macraes (> 125 t Au). Geochemical and Nd isotopic similarities between the samples point to a common history of the two terranes rather than the amalgamation of one or two allochthonous plate fragments. Furthermore, geochemical and Nd data suggest the metabasalts within both terranes formed in an oceanic but essentially non-subduction-related setting. The origin of the Aspiring and Torlesse basalts can be linked to the formation of an oceanic plateau that had resulted from a (?Permian) mantle plume initiation event proximal to a mid-oceanic rise or triple junction. Given the intrinsically gold-enriched nature of certain oceanic-character mafic rocks, the anomalous gold endowment of the Otago Schist may have been enhanced via the accretion and subduction of a gold-enriched oceanic plateau fragment. The metabasalts are generally enriched in gold (up to 13 ppb) compared to their enclosing metasedimentary rocks (typically ca. 1 ppb), with sulphide-rich metabasaltic rocks having up to 550 ppb Au. However, the relatively small volume of metabasalts in the Otago Schist precludes these rocks as the principal source for Otago Schist orogenic gold, with a primarily metasedimentary source of the gold potentially having a limiting effect on the overall endowment of the Otago Schist. This approach, that employs petrogenetic fingerprinting of potentially fertile source rocks for the assessment of gold endowment, might prove useful in the conceptual exploration targeting of relatively immature and poorly exposed terrains. 相似文献
16.
17.
小秦岭金矿田太古宙太华群变质岩与金矿关系的探讨 总被引：1，自引：0，他引：1
小秦岭金矿田变质岩是由表壳岩经过区域变质、深部重熔、混合岩化作用形成,典型特征是低钾富钠,具有太古宙TTG岩石特点.Au元素在太华群岩层、岩石中分布不均匀、多重母体分布是造成现今太华群金丰度值低的一个重要原因.Au元素在太华群地层和侵入于其中的花岗质岩石遭受变质及混合岩化作用过程中曾经历了非均一化作用并产生早期活化转移,在一些部位贫化,在一些部位富集,富集部位就可能形成矿床.硫、铅同位素的对比研究,证实了成矿物质来源于该套古老变质岩系. 相似文献
18.
Akira Imai Kotaro Yonezu Kenzo Sanematsu Takashi Ikuno Shingo Ishida Koichiro Watanabe Visut Pisutha‐Arnond Somchai Nakapadungrat Jarupong Boosayasak 《Resource Geology》2013,63(1):84-98
Geochemical studies were conducted on the hydrothermally altered granitic rocks in the Ranong and Takua Pa tin‐fields in southern Thailand in order to investigate the mode of occurrence of REE (rare earth elements), with emphasis placed on a potential REE resource associated with granitic rocks in the Southeast Asian Tin Belt. The total REE (ΣREE) content of altered granitic rocks ranges from 130 to 350 ppm at Haad Son Paen (which is presently mined for kaolin clay) in the Ranong tin‐field, and that of altered granitic rocks and kaolinite veinlets reaches up to 424 ppm and 872 ppm, respectively, at Nok Hook in the Takua Pa tin‐field. Rare earth elements in the altered granitic rocks and kaolinite veinlets show a relatively flat chondrite‐normalized pattern, thus enriched in heavy REE compared with the original granitic rocks and their weathered crusts. At Nok Hook (Takua Pa), the ΣREE content of kaolinite separated from an altered granitic rock by elutriation is 1313 ppm, a ΣREE amount about four times higher than that of whole‐rock composition of the altered granitic rock. Chondrite‐normalized REE patterns of the elutriated kaolinite and of the altered granite are relatively flat. Sequential extraction experiments suggest that 41 and 85 percent of REE are present as ion exchangeable‐form in the altered granitic rock, and in the kaolinite veinlets, respectively. In addition, more than 90% of REE in the kaolinite veinlets are present as the acid‐soluble state. On the other hand, the ΣREE content of kaolinite veinlets and of the kaolinite concentrated by elutriation from an altered granitic rock at Haad Som Paen (Ranong) is 70 ppm and 75 ppm, respectively, thus enrichment of REE in kaolinite was not confirmed. In addition, by the sequential extraction experiments, 23% and 4% of REE were extracted from the altered granitic rock and the kaolinite veinlets at Haad Som Paen. In the altered granitic rocks at Haad Som Paen, REE are present as refractory phases, and REE in the acid‐soluble states had been leached by hydrothermal fluid. 相似文献
19.
The Xihuashan and Tieshanlong tungsten deposit is an important large quartz vein‐type W‐polymetallic deposit in the southern Jiangxi Province, eastern Nanling Range. Zircon U–Pb analyses of representative ore‐forming granites from the Xihuashan and Tieshanlong tungsten deposit yield ages of 146.3 ± 2.9 Ma and 146.0 ± 3.8 Ma, respectively. According to the zircon Raman spectroscopy, these granitic rocks are disturbed by different degrees of hydrothermal alteration, whereas most zircons exhibit primary oscillatory zoning and Th/U ratios in the range of magmatic zircon, which means the analysis results represent the crystallization age of metallogenetic granitic assemblages. In combination with regional geological data, it is suggested that the Late Jurassic is probably another important episode of granitic magmatism and W‐Sn mineralization in southern Jiangxi Provinces, even South China. 相似文献
20.
胶东是我国最大的金矿集区,已探明金资源储量5000余吨。招平断裂带是胶东地区重要的控矿断裂,通常将其分为北、中、南三段,其中北段、中段目前都赋存大型-特大型金矿床,而南段仅有几个小型矿床。为揭示该断裂带的关键控矿因素,评估其南段成矿潜力,本文以招平断裂带南段为研究对象,通过元素相关性和聚类分析,确定成矿元素共生组合,进而圈定成矿有利地段。结果显示：Au、Bi、Pb、Ag等元素在绢英岩化碎裂岩、绢英岩化花岗质碎裂岩、碎裂状花岗岩中明显富集;糜棱岩中各元素含量与围岩大致相当,富集不明显。相关性分析和聚类分析显示,Au与Bi、Ag、Hg聚为一类,相关性好,是成矿的指示元素。与北段、中段相比,南段糜棱岩和构造片岩发育,南段由南向北韧性变性作用变弱,而脆性破碎逐渐变强。金矿的形成与脆性碎裂关系密切,韧性变形不利于金矿的形成。研究认为南段的北端、南端成矿条件好,具有较好的找矿潜力,而中部不利于成矿,找矿前景不大。 相似文献