东秦岭伟晶岩型高纯石英矿地球化学、锆石U-Pb及Hf同位素研究:对高纯石英找矿方向的探讨

Geochemistry,zircon U−Pb and Hf isotopes of the high−purity pegmatite−quartz deposits in the Eastern Qinling and discussion on its prospecting direction

[研究目的]高纯石英是战略性新兴产业的关键基础材料,是世界稀缺的战略性矿产资源。目前美国以Spruce-Pine花岗伟晶岩作为原料生产的4N8及以上高端石英砂产品几乎垄断国际市场。东秦岭4N级伟晶岩型高纯石英矿点的发现为研究高纯石英形成机制、实现找矿突破和建立成矿模型提供了难得的机遇。[研究方法]通过对东秦岭新发现的伟晶岩型高纯石英矿点开展野外调查,并与美国Spruce-Pine高纯石英矿床伟晶岩开展岩石地球化学、锆石U-Pb同位素年代学和Hf同位素等方面的对比研究。[研究结果]东秦岭10号高纯石英矿形成于早泥盆世,锆石U-Pb年龄为(406.8±0.8)Ma,稍早于美国Spruce-Pine的高纯石英花岗伟晶岩形成时代。东秦岭高纯石英矿点伟晶岩与美国Spruce-Pine高纯石英矿床伟晶岩形成温度均为600℃左右。东秦岭高纯石英矿点伟晶岩与美国Spruce-Pine高纯石英矿床伟晶岩具有相似的岩石地球化学特征,表现I型花岗岩和高分异演化特征,源区物质来源既有下地壳,也有幔源物质。仅通过对东秦岭高纯石英矿点伟晶岩和灰池子花岗岩体空间关系、形成时代和岩石地球化学特征,是不足以完全反演源区特征及成岩成矿过程,对于东秦岭高纯石英矿点伟晶岩和灰池子花岗岩体是否存在同源演化仍需要进一步研究。[结论]东秦岭与美国Spruce-Pine高纯石英矿床在花岗岩类型、岩浆特征和形成温度等方面具有相似性,为进一步揭示高纯石英成矿地质背景和实现找矿突破提供理论依据。

[Objective]As the world's scarce strategic mineral resource,high−purity quartz is the key basic material of strategic emerging industries.Spruce−Pine granitic pegmatite was used as raw material by the United States to produce high−end quartz sand products,which were better than the quality of 4N8,and almost monopolized the international market.The discovery of 4N class high−purity pegmatite−quartz deposits in Eastern Qinling provides a rare opportunity to study the formation mechanism of high purity quartz,realize prospecting breakthrough and establish metallogenic model.[Methods]Based on the field investigation of the newly discovered high−purity pegmatite-quartz deposits in the Eastern Qinling Mountains,the geochemistry,zircon U−Pb isotope chronology and Hf isotope of pegmatite deposits in Spruce−Pine high−purity quartz deposits in the United States were compared.[Results]The Eastern Qinling 10 high purity quartz deposit was formed in the Early Devonian with a zircon U−Pb age of(406.8±0.8)Ma,which is earlier than that of high purity quartz granite−pegmatite in Spruce−Pine.The formation temperature of pegmatite from high purity quartz deposit in Eastern Qinling and Spruce−Pine is about 600℃.Pegmatite from the high purity quartz deposit in the Eastern Qinling has similar geochemical characteristics to pegmatite from the high purity quartz deposit in Spruce−Pine,showing features of I-type granite and high differentiation evolution.The materials in the source area come from both lower crust and mantle.It is not enough to completely invert the characteristics of the source area and the diagenesis and mineralization process by compared the spatial relationship with formation age and petrogeochemical characteristics.Whether the pegmatite of high purity quartz deposits and Huichizi granite pluton in the Eastern Qinling have the homologous evolution still needs further study.[Conclusions]Compared with the granite type,magmatic characteristics and formation temperature of the high−purity quartz deposits(points)in the Eastern Qinling and Spruce−Pine are similar,which provides a theoretical basis for further revealing the geological background of high−purity quartz mineralization and achieving breakthroughs in high−purity quartz ore deposits prospecting.