| 蚀变岩帽的特征、成因以及在华南的分布探讨 |
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| 引用本文： | 陈静,周涛发,张乐骏,孙艺,WHITE Noel C,李旋旋.蚀变岩帽的特征、成因以及在华南的分布探讨[J].岩石学报,2020,36(11):3380-3396. |
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| 作者姓名： | 陈静 周涛发 张乐骏 孙艺 WHITE Noel C 李旋旋 |
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| 作者单位： | 合肥工业大学资源与环境工程学院, 合肥工业大学矿床成因与勘查技术研究中心, 合肥 230009;Centre for Ore Deposit and Earth Sciences, University of Tasmania, Hobart 7001;合肥工业大学资源与环境工程学院, 合肥工业大学矿床成因与勘查技术研究中心, 合肥 230009;安徽省矿产资源与矿山环境工程技术研究中心, 合肥 230009 |
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| 基金项目： | 本文受国家重点研发计划项目（2016YFC0600206）和国家自然科学基金项目（91962218、41320104003）联合资助. |
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| 摘 要： | Sillitoe（1995）蚀变岩帽（Lithocap）的定义为大范围富黄铁矿的硅化、高级泥化和泥化蚀变，在地质环境上位于古地表和浅成中-酸性岩浆侵入体之间。蚀变岩帽往往显示为突出的正地形，有助于寻找隐伏的斑岩矿化体。但蚀变岩帽在地表的范围往往多达几十个平方千米，又常常掩盖下覆斑岩矿床的蚀变矿化特征及其地球化学印记，因此大型的蚀变岩帽又给勘探工作带来一定的挑战。蚀变岩帽相关矿床的勘探需以地质填图为基础，结合近红外光谱分析（SWIR）进行蚀变填图，以及全岩地球化学以及矿物地球化学表现的元素或元素组合异常，来帮助定位热源或深部斑岩体。遥感和地球物理中的激电响应，也可以辅助定位岩体。华南地区的蚀变岩帽主要分布于长江中下游成矿带和东南沿海火山岩带。前人对安徽庐枞盆地中的矾山蚀变岩帽进行了系统研究，确定了矾山蚀变岩帽形成于白垩纪，与围岩砖桥组火山岩年龄一致。同位素和流体包裹体工作证明了形成矾山蚀变岩帽的流体主要为深部岩浆热液中的酸性气体与浅部大气降水的混合，在浅部高渗透率的火山岩及其岩性界面反应，广泛发育了一套硅化和高级泥化蚀变，指示与矾山相关可能存在斑岩和高硫型浅成低温热液铜金矿床。福建紫金山地区有中国最大的高硫型浅成低温热液矿床，主要赋存于紫金山蚀变岩帽中。紫金山蚀变岩帽的地质特征和蚀变分带已经研究的较为详细，但目前深部的侵入体还没有发现。浙江的蚀变岩帽是中国非金属矿产的重要来源，包括明矾石矿、地开石矿和红柱石矿等，这些蚀变岩帽与金属矿化的关系尚未有相关研究。根据目前的资料总结，有较多的蚀变岩帽分布在中国华南，这些蚀变岩帽特征典型，但目前的研究程度尚浅。现有的研究结果表明，华南的蚀变岩帽的成矿潜力巨大，可能存在一条巨型的斑岩-浅成低温矿床成矿带，具有广阔的找矿勘查前景，建议加强蚀变岩帽及相关矿床的找矿与研究工作。
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| 关 键 词： | 蚀变岩帽 华南 明矾石 地球化学特征 高级泥化蚀变 |
| 收稿时间： | 2019/12/4 0:00:00 |
| 修稿时间： | 2020/9/20 0:00:00 |
A discussion of characteristics, genesis of lithocaps and their distributions in South China |
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| CHEN Jing,ZHOU TaoF,ZHANG LeJun,SUN Yi,WHITE Noel C,LI XuanXuan.A discussion of characteristics, genesis of lithocaps and their distributions in South China[J].Acta Petrologica Sinica,2020,36(11):3380-3396. |
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| Authors: | CHEN Jing ZHOU TaoF ZHANG LeJun SUN Yi WHITE Noel C LI XuanXuan |
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| Institution: | School of Resources and Environmental Engineering, Ore Deposits and Exploration Centre, Hefei University of Technology, Hefei 230009, China;Centre for Ore Deposit and Earth Sciences, University of Tasmania, Hobart 7001, Australia;School of Resources and Environmental Engineering, Ore Deposits and Exploration Centre, Hefei University of Technology, Hefei 230009, China;Anhui Province Engineering Research Centre for Mineral Resources and Mine Environments, Hefei 230009, China |
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| Abstract: | The lithocap, as first defined by Sillitoe (1995), is a volumetrically significant domain of pyrite-rich rocks with extensive hypogene silicic, advanced argillic and argillic alterations that formed between a paleosurface and a shallow-crustal intrusion. It is helpful for the finding of underlain porphyry mineralizations by a lithocap due to its prominence on the surface. However, the presence of a large lithocap (developed in an area over tens of square kilometres) together with an extensive hydrothermal alteration may obscure the geochemical footprint of the underlying porphyry deposits since it''s difficult to further define the location of the underlying intrusive center. The exploration of location of mineralization within, under, or adjacent to a large lithocap must on the basis of detailed geological mapping, including the alteration mapping, with the aid of short-wave infrared spectroscopy (SWIR) analyses. The anomaly of elements in the whole rock geochemistry and mineral chemistry can provide directional indicators for locating the heat source or underlying intrusion. Remote sensing and induced polarization (IP) surveys were used to help site drill holes. Lithocaps in South China are mainly distributed in the Middle-Lower Yangtze Belt (MLYB) and the Coastal Volcanic Belt. Previous studies about Fanshan lithocap in Luzong basin, Anhui Province, indicate that it was formed simultaneously with its host volcanic rocks in Cretaceous. The fluid inclusion study, especially the O-D isotopes of the quartz, proved that the fluids that form the Fanshan lithocap are a mixture of magmatic-hydrothermal fluid with meteoric water, where the fluids reacted with the permeable volcanic rocks, and the lateral outflows help to develop such an extensive silicic and advanced argillic alteration. There are high potentials for finding the high sulfidation epithermal and porphyry deposits in Fanshan and Luzong basin. Another case of a lithocap occured at Zijinshan district, Fujian Province, where the biggest high sulfidation epithermal deposit developed in China. The geological and alteration characteristics of this deposit have been systematic studied, but the underlain porphyry has not been determined by any exploration yet. Lithocaps in Zhejiang Province have provided a large amount of non-metallic resources in China, including alunite, dickite, pyrophyllite and andalusite, however, the relationships between these lithocaps and the metal deposits have not been examined yet. In general, a large amount of lithocaps are distributed in South China, and they have typical alteration characteristics of a lithocap, but the studies of these lithocaps are still limited. The current researches indicate that mineralization related to lithocaps in South China has a tremendous potential, which possibly forms a giant porphyry epithermal metallogenic belt. Further studies should focus on explorations in, below or adjacent to these lithocaps. |
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| Keywords: | Lithocap South China Alunite Geochemical characteristics Advanced argillic alteration |
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