Fluid inclusion and H–O isotope evidence for immiscibility during mineralization of the Yinan Au–Cu–Fe deposit, Shandong, China

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• 作者：Y.M. Zhang^a ; X.X. Gu^a ; ^{xuexiang_gu@cugb.edu.cn"" rel=""nofollow} ; L. Liu^a ; S.Y. Dong^a ; ^b ; K. Li^c ; B.H. Li^b ; P.R. Lv^a
• 关键词：Immiscibility ; Boiling ; Fluid inclusion ; H&#x2013 ; O isotopes ; Yinan Au&#x2013 ; Cu&#x2013 ; Fe deposit ; Shandong
• 刊名：Journal of Asian Earth Sciences
• 出版年：2011
• 出版时间：10 July 2011
• 年：2011
• 卷：42
• 期：1-2
• 页码：83-96
• 全文大小：2666 K

文摘

The fluid inclusion and H&#x2013;O isotope studies have provided the evidences for the source of ore-forming fluids, and helped to recognize two types of immiscibility and their relationships with mineralization. Hydrogen and oxygen isotopic geochemistry shows that the earlier ore-forming fluids during the anhydrous skarn stage (I) and the hydrous skarn-magnetite stage (II) were mainly derived from magmatic water, while the later fluids during the quartz-sulfide stage (III) and the carbonate stage (IV) were mainly from magmatic water mixed with small amounts of meteoric water. Various types of fluid inclusions, including abundant vapor- or liquid-rich two-phase aqueous inclusions, daughter minerals-bearing multiphase inclusions, CO₂&#x2013;H₂O inclusions, and less abundant liquid inclusions, vapor inclusions and melt inclusions, are present in hydrothermal minerals of different stages. The liquid&#x2013;vapor fluid inclusions are mainly composed of H₂O, with significant amounts of CO₂ and a small amount of CH₄. In the opaque-bearing fluid inclusions, the hematite and fahlore (tetrahedrite) were identified. The homogenization temperature of the aqueous fluid inclusions decreases from Stage I (520&#x2013;410 °C), through Stage II (430&#x2013;340 °C) and III (250&#x2013;190 °C), to Stage IV (190&#x2013;130 °C). The coexistence of melt inclusions with simultaneously trapped vapor- or liquid-rich two-phase aqueous inclusions and daughter minerals-bearing multiphase inclusions in garnet, diopside and epidote of Stages I and II suggests an immiscibility between silicate melt and hydrothermal fluid. It is an effective mechanism on scavenging and transporting ore-forming components from magmas. The aqueous fluid inclusions with various vapor/liquid ratios (from <10 % to >65 % ) commonly coexist with simultaneously trapped liquid inclusions, vapor inclusions, daughter minerals-bearing multiphase inclusions and CO₂&#x2013;H₂O inclusions in the quartz of Stage III, and the different kinds of the fluid inclusions have similar homogenization temperatures. This indicates that the boiling &#x2013; another kind of immiscibility, widely took place during Stage III. It resulted in the precipitation and enrichment of gold, copper and iron.