云英岩在开放与封闭岩浆体系中成因差异性的对比研究——以南岭成矿带四个代表性含钨和含锂矿床为例  

Difference study of greisen formation between open and closed magmatic systems:Example from four representative W-and Li-bearing deposits in the Nanling metallogenic belt

作　　者：龚磊 郭春丽[2,3] 于淼[1] 郑义 张斌武 陈振宇[2] 马星华 许以明 GONG Lei;GUO ChunLi;YU Miao;ZHENG Yi;ZHANG BinWu;CHEN ZhenYu;MA XingHua;XU YiMing(Central South University,Changsha 410083,China;MNR Key Laboratory of Metallogeny and Mineral Assessment,Institute of Mineral Resources,Chinese Academy of Geological Sciences,Beijing 100037,China;SinoProbe Laboratory,Chinese Academy of Geological Sciences,Beijing 100094,China;Investigation of Mineral Resources of Hunan Province,Chenzhou 423000,China)

机构地区：[1]中南大学,长沙410083 [2]成矿作用与资源评价自然资源部重点实验室,中国地质科学院矿产资源研究所,北京100037 [3]自然资源部深地科学与探测技术实验室,中国地质科学院,北京100094 [4]湖南省矿产资源调查所,郴州423000

出　　处：《岩石学报》2024年第9期2905-2924,共20页Acta Petrologica Sinica

基　　金：国家自然科学基金重点项目(92162210);面上项目(42172096)联合资助.

摘　　要：云英岩是花岗质岩浆成岩和成矿过程中常见的岩石类型,也是有色和稀有金属元素的主要赋矿体。目前对其成因主要有三种认识:由花岗质熔体与外界流体交代而成、花岗质熔体与岩浆出溶热液相互作用的产物、以及高度富Li-F的特殊中酸性岩浆岩。为了进一步阐明云英岩的形成机制,本研究聚焦南岭成矿带晚侏罗世(166~145Ma)包括淘锡坑石英脉型W矿床、柿竹园矽卡岩-云英岩型W-Sn-Mo-Bi-F矿床、茅坪石英脉-云英岩型W-Sn-Li矿床、香花铺花岗岩型W-Ta-Nb-Li矿床在内的四个花岗质岩浆-液热矿床,通过对侵入岩体的花岗岩、云英岩化花岗岩和云英岩中不同类型云母的EMPA和LA-ICP-MS分析,发现:(1)淘锡坑和柿竹园W矿床中云英岩的云母为多硅白云母,而茅坪和香花铺含W-Li矿床中云英岩的云母为铁锂云母;(2)淘锡坑和柿竹园从低分异花岗岩→高分异花岗岩→云英岩,其SiO 2、Al 2O 3含量并未呈现一直增加或降低的趋势,而是出现一个转折;而茅坪和香花铺云母中的上述主量元素变化趋势一致,未出现转折,说明它们在岩浆演化上具有一定的差异性;(3)淘锡坑和柿竹园中云母的Ba含量突然增加表明有外界流体加入,而茅坪和香花铺云母中的Ba含量保持不变,说明体系基本维持在封闭状态。本研究认为,导致上述差异性的原因是由于淘锡坑和柿竹园的钨矿体是在开放体系下,花岗质熔体与外来流体发生相互作用而形成的;茅坪云英岩钨锂矿是在半封闭体系下熔体-流体共存阶段形成的,主要为岩浆自身出溶热液且有少量大气降水加入;而香花铺锂矿是在几乎全封闭体系下由岩浆与自身出溶热液相互作用的产物。本研究提出钨和锂元素的富集均需要岩浆经历高度分异作用,岩浆体系是否开放是形成何种矿产的重要条件。Greisen is a prevalent rock type that formed during the granitic magmatism and mineralization and is a primary ore body for non-ferrous and rare metals.At present,there are three types of understanding to its generation:Metasomatism between the granitic melt and external fluid,interaction between the granitic melt and magmatic hydrotherm,and a special magmatic rock with very high Li-F contents.To further explain the formation mechanism of greisen,four Late Jurassic magmatic-hydrothermal deposits in the Nanling metallogenic belt were selected in this work.They are Taoxikeng quartz vein-type W deposit,Shizhuyuan skarn-greisen type W-Sn-Mo-Bi-F deposit,Maoping quartz vein-greisen type W-Sn-Li deposit,and Xianghuapu granite-type W-Ta-Nb-Li deposit.By studying the different categories of mica from the granite,greisenized granite,and greisen through the EMPA and LA-ICP-MS analyses,we found that:(1)The mica in greisen from the Taoxikeng and Shizhuyuan deposits are phengite;while the mica in greisen from the Maoping and Xianghuapu deposits are zinnwaldite;(2)From the lowly fractionated granite→the highly fractionated granite→greisen,the SiO 2,Al 2O 3 compositions in mica from the Taoxikeng and Shizhuyuan deposits take a turn rather than always increasing or decreasing trend,but these contents in mica from the Maoping and Xianghuapu deposits show a consistently changing tendency,it shows that they have certain differences in magma evolution.We considered that the reasons for above changes is due to:(1)the greisens in the Taoxikeng and Shizhuyuan deposits were formed during the interaction between the granitic melt and the external fluid in the open system of magma reservoir;(2)the greisens in the Maoping and Xianghuapu deposits were generated during the stage of melt-fluid coexistence,and the fluids came from the magmatic exsolution and minor addition of the meteoric water.Therefore,we suggested that:(1)the W-and Li-element enrichment all required the highly fractionated magmas which experienced a certain degree of cr

关 键 词：云英岩 云母微量元素 矽卡岩型钨矿 石英脉型钨锂矿 花岗岩型锂矿 晚侏罗世 南岭成矿带 

分 类 号：P588.121[天文地球—岩石学] P618.67[天文地球—地质学] P618.71