投稿时间：2018-01-02
修订日期：2018-04-26
网络发布日期：2019-03-02
中文摘要:折腰山矿床是甘肃省白银厂矿田内最典型的火山成因块状硫化物（VMS）矿床，赋矿围岩主要为奥陶纪石英角斑凝灰岩，属于FⅡ类流纹岩，为弧后环境的产物，在海底对流循环成矿作用过程中，遭受强烈的热液改造，形成了多种类型的蚀变。文章将折腰山矿床蚀变围岩分为弱蚀变带→绢云母硅化带→绿泥石化带→矿化带，利用蚀变趋势图解和质量迁移计算等方法，定量揭示了热液蚀变过程中元素的迁移规律。研究表明：①从弱蚀变带→矿化带，蚀变强度逐渐增大，主量元素P、Mn有一定活动性，二者的迁移量分别为-8.8%~8.8%和-1.8%~9.9%，但迁移趋势不规律；Si迁移量变化范围较大，为-16.2%~83.73%；Na、Ca、Sr大量迁出，其中Na、Ca最大迁出量分别可达-3.11%和-2.71%；Mg、Fe依次迁入，并在绿泥石化带中达到最大值9.49%和69.73%；K在绢云母化带中迁入量出现峰值1.6%，其后逐渐迁出，最大可达-2.22%；Rb的迁移行为与K一致；②高场强元素Nb、Ta、Zr、Hf等在热液蚀变过程中相对保持惰性；Al、Ti及Y表现为弱活动性；③主要成矿元素Cu随蚀变强度的增大，其迁入量有递增的趋势，Pb、Zn在矿化带中迁入，其余各带均为迁出；④热液活动过程中，SiO2活化再沉淀，形成硅化蚀变；K的迁入形成绢云母化，并消耗了H+，使热液酸度减小；Mg、Fe的迁入在还原环境下形成绿泥石化，并伴随金属硫化物的沉淀。因此，折腰山矿床中的绿泥石化可能是导致矿质发生沉淀的重要蚀变作用，其在勘查工作中可以作为寻找VMS矿体的重要标志。
Abstract:The Zheyaoshan deposit is the most typical volcanogenic massive sulfide (VMS) deposit in Baiyinchang orefield, Gansu Province. The deposit mainly occurs in the Ordovician quartz keratophyre tuff, which belongs to the FⅡ-type rhyolite, and originated from a back-arc tectonic setting. In the process of seafloor convection circulation mine ralization, the rocks suffered from intense hydrothermal transformation which resulted in many types of alteration. In this paper, the altered rocks in Zheyaoshan deposit are subdivided into least-altered zone, sericitation-silicification zone, chloritization zone and mineralization zone. By means of migration trend diagram and mass change calcula-tion, the authors quantitatively interpret the migration regularity of elements in the process of hydrothermal alteration. Some conclusions have been reached:① The alteration intensity gradually increases from least-altered zone to mineralization zone. Major elements P, Mn show some activity with a variation from -8.8% to 8.8% and from -1.8% to 9.9% respectively but have irregular migration trend; Si has a diverse migration, which ranges from-16.2% to 83.73% of the mass; Na, Ca, Sr are strongly depleted, Na and Ca have been lost by -3.11% and -2.71%; Mg, Fe move in gradually and have gain as much as 9.49% and 69.73% in the chloritization zone; K shows a peak value of 1.6% in sericitization zone, and then gradually moves out by -2.22% in late hydrothermal alteration zone, the migration behavior of Rb is consistent with that of K; ② High field strength elements (e. g., Nb, Ta, Zr and Hf et al.) behave relatively inertly in the process of hydrothermal alteration; Al, Ti and Y are characterized by slight activity; ③ Metallogenic element Cu has a tendency of increasing enrichment following increasing alteration intensity, Pb, Zn are enriched in the mineralization zone but are leached out in other alteration zones; ④ During the hydrothermal alteration, SiO 2 experiences a process of activation and precipitation, then forms the silicification alteration; The gain of K forms sericitization and consumes the H+, resulting in the decrease of hydrothermal acidity; And the gain of Mg, Fe forms chloritization under reductive environment, along with the metal sulfide precipitation in the same time. Therefore, chloritization in Zheyaoshan deposit is an important alteration type that may give rise to mineral precipitation, and can hence be used as a significant symbol of VMS orebodies in the exploration.
keywords:geology VMS deposit hydrothermal alteration element migration mass change calculation Baiyinchang Gansu Province
文章编号：
中图分类号：P618.41;P614
文献标志码：
基金项目:中国地质调查局项目（编号：12120114050101）资助
引用文本：
田光礼,陈守余,董凯,赵江南,覃伟,陈俊霖.2019.甘肃白银厂折腰山VMS矿床蚀变带元素迁移及定量计算[J].矿床地质,38(1):80~100TIAN GuangLi,CHEN ShouYu,DONG Kai,ZHAO JiangNan,QIN Wei,CHEN JunLin.2019.Elements migration and mass change calculations in alteration zones of Zheyaoshan VMS deposit, Baiyinchang, Gansu Province[J].Mineral Deposits38(1):80~100
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