| 王红军.青海省绿梁山铜矿成因新证据
—来自硅质岩地球化学特征及其沉积环境[J].地质与勘探,2017,53(1):63-77 |
| 青海省绿梁山铜矿成因新证据
—来自硅质岩地球化学特征及其沉积环境 |
| Genesis of the Lüliangshan copper deposit in Qinghai Province: New evidence from geochemical characteristics and sedimentary environment of cherts |
| 投稿时间：2016-08-31 修订日期：2016-10-12 |
| DOI：10.12134/j.dzykt.2017.01.007 |
| 中文关键词: 硅质岩 地球化学特征 沉积环境 绿梁山铜矿 VMS型 |
| 英文关键词: chert,geochemical characteristic,sediment environment, Lvliangshan copper deposit,VMS-type,Qinghai Province |
| 基金项目:中国地质调查局矿产远景调查项目（编号：1212011121204）、中国地质调查局调查评价项目（编号：12120113032800）资助。 |
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| 中文摘要: |
| 在绿梁山铜矿区发育有厚度0.1~2m不等的硅质岩，与该区铁铜矿化关系较为密切，为了解其与铜矿床成因之间的关系，对硅质岩进行了岩石地球化学分析和沉积环境恢复。岩石地球化学分析结果表明： SiO2含量和 Si/ Al比值说明该区硅质岩主要为不纯的硅质岩；SiO2-Al2O3和Fe-Mn-Al图解反映硅质岩主要为热水成因，Al/(Al+Fe+Mn)、Fe/Ti、（Fe+Mn）/Ti、Co/Ni、U/Th等比值，均显示出热水沉积硅质岩的特点； K2O/Na2O、Al2O3/TiO2比值符合以偏基性中性火山岩为源区的海底火山作用形成的硅质岩的特征，V/Cr、Co/Ni比值也指示硅质岩在形成过程遭受了中基性岩浆作用的影响，硅质岩与该区玄武安山岩相似的稀土元素特征及Eu的无或弱的正异常，表明其形成与海底火山热液关系密切，并有海水的参与；ΣREE较低， HREE富集，Ce表现出负异常， (La/Ce)N值等都说明硅质岩形成于大洋盆地环境，Zr、Hf、Nb、Ta等HFSE强烈亏损，K、Rb、Ba等HILE强烈富集，与岛弧火山岩微量元素蛛网图一致，说明其形成于岛弧或弧后盆地，并且受陆源物质的影响较小。结合该矿床的基本地质特征可以认为该区硅质岩是火山热液或喷气活动在海底间歇式喷发或旋回期喷发的热水沉积产物，指示绿梁山铜矿为经后期造山改造的VMS型矿床，硅质岩可以作为该区有效的找矿标志，明确下一步找矿目标应试寻找火山喷发的通道和破火山口，以寻找其可能存在的主矿体。 |
| 英文摘要: |
| Some kinds of cherts with thicknesses ranging 0.1~2m are present in the Lüliangshan copper deposit of Qinghai Province, which have a close relationship with mineralization located in the lower portion of the cherts as interlayers in the volcanic rocks.Geochemical analysis of cherts sandwich shows characteristics as follows: The content of SiO2 and Si/Al indicates that they are not pure cherts. SiO2-Al2O3 and Fe-Mn-Al diagrams indicate cherts are of hydrogenous genesis. The ratios of Al/(Al+Fe+Mn), Fe/Ti,（Fe+Mn）/Ti, Co/Ni and U/Th show they came from hydrogenous. The ratios of K2O/Na2O and Al2O3/TiO2 are similar to the characteristics of the siliceous rocks of submarine volcanoes whose source came from the partial basic volcanic rocks. V/Cr and Co/Ni also indicate the cherts experienced influence of medium basic magma activity. The characteristics of REE between cherts and basaltic andesite are similar, which also have a weak abnormal δEu, indicating the cherts’s formation has a close contact with basic submarine volcanic hydrothermal. Meanwhile the sea water was involved.ΣREE is low,and the REE distribution curves are inclined to the left and HREE is enriched. The negative δCe anomaly and the ratio of (La/Ce)N all show that the cherts formed in an ocean basin environment. The lower content of Zr, Hf, Nb and so forth ,which is HFSE, and the higher content of Rb, K, and Sr, which are LILE, suggest that the cherts have a similar environment with IAB. The terrigenous matter has little impact on their formation. Combined with the basic geological characteristics, we can conclude that the cherts are hydrothermal sediments which formed during eruption intervals of volcanic activities under sea or intermittent of volcanic cycles. The Lüliangshan copper deposit is of a VMS-type, which was subjected to orogenic transformation in the later stage. The cherts can be regarded as an ore-prospecting criterion. Next step is to explore the volcanic eruptions channels and the caldera to search for the potential main ore bodies. |
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