Fluid bubbles in melt inclusions and pillow-rim glasses: high-temperature precursors to hydrothermal fluids?
Fluid bubbles in melt inclusions and pillow-rim glasses: high-temperature precursors to hydrothermal fluids?
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DOI：
10.1016/s0009-2541(01)00383-7
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发表时间：
2002-03
期刊：
影响因子：
3.9
通讯作者：
Vadim Kamenetsky;P. Davidson;T. Mernagh;A. Crawford;J. Gemmell;M. Portnyagin;R. Shinjo
中科院分区：
文献类型：
--
作者：
Vadim Kamenetsky;P. Davidson;T. Mernagh;A. Crawford;J. Gemmell;M. Portnyagin;R. Shinjo
许多类型的热液矿床的形成假说往往涉及与岩浆有关的流体的直接贡献（例如，Cu-Mo-Au斑岩）或它们叠加在贫瘠的热液细胞上（例如，火山岩型块状硫化物矿床）。然而，这些流体的化学和相组成仍然在很大程度上未知。我们报告了对来自不同构造环境（包括大洋中脊）的玄武岩浆中的原始橄榄石斑晶和枕边玻璃中的玻璃质熔体包裹体中捕获的流体气泡进行全面研究的初步结果（麦考瑞岛，西南太平洋和大西洋中脊43°N断裂带），海洋岛屿（夏威夷）和各种现代和古代后弧-岛弧环境（马努斯盆地东部、冲绳和瓦努阿图海槽、特罗多斯、新喀里多尼亚和猎人脊-猎人断裂带）。利用电子显微镜和EDS及激光拉曼光谱研究了来自各地的流体气泡，发现它们由含CO2-（±H2O±硫）的蒸气组成，并含有大量的非晶相（Na-K-Ca-Fe铝硅酸盐和溶解的碳）和结晶相。晶体主要以碳酸盐（菱镁矿、方解石、铁白云石、白云石、菱铁矿、苏打石和菱锰矿）、硫酸盐（硬石膏、石膏、重晶石和角闪石）和硫化物（黄铁矿、毒砂、黄铜矿和白铁矿）为代表，但也可能出现其他矿物（水镁石、磷灰石、岩盐、斜顽辉石、六方钾霞石、霞石、角闪石和云母）。我们认为，化学成分（例如，C、H、S、Cl、Si、Al、Na、K、Fe、Mn、Cr、Ca、Mg、Ba、Pb和Cu）最初溶解在岩浆流体中，在包埋后没有由基质玻璃或斑晶提供。富含溶解金属和其他非挥发性元素的岩浆流体可能是成矿溶液的潜在前驱体。
Hypotheses for the formation of many types of hydrothermal ore deposits often involve the direct contribution of magma-related fluids (e.g., Cu–Mo–Au porphyries) or their superimposition on barren hydrothermal cells (e.g., volcanic-hosted massive sulfide deposits). However, the chemical and phase compositions of such fluids remain largely unknown. We report preliminary results of a comprehensive study of fluid bubbles trapped inside glassy melt inclusions in primitive olivine phenocrysts and pillow-rim glasses from basaltic magmas from different tectonic environments, including mid-ocean ridges (Macquarie Island, SW Pacific and Mid-Atlantic Ridge 43°N Fracture Zone), ocean islands (Hawaii) and a variety of modern and ancient backarc–island arc settings (eastern Manus Basin, Okinawa and Vanuatu Troughs, Troodos, New Caledonia and Hunter Ridge–Hunter Fracture Zone). Fluid bubbles from all localities, studied using electron microscopy with EDS and laser Raman spectroscopy, are composed of CO2-(±H2O±sulfur)-bearing vapor and contain significant amounts of amorphous (Na–K–Ca–Fe alumino-silicates and dissorded carbon) and crystalline phases. The crystals are represented mainly by carbonates (magnesite, calcite, ankerite, dolomite, siderite, nahcolite and rhodochrosite), sulfates (anhydrite, gypsum, barite and anglesite), and sulfides (pyrite, arsenopyrite, chalcopyrite and marcasite), though other minerals (brukite, apatite, halite, clinoenstatite, kalsilite, nepheline, amphibole and mica) may occur as well. We argue that chemical components (e.g., C, H, S, Cl, Si, Al, Na, K, Fe, Mn, Cr, Ca, Mg, Ba, Pb and Cu) that later formed precipitates in fluid bubbles were originally dissolved in the magmatic fluid, and were not supplied by host glasses or phenocrysts after entrapment. Magma-related fluid rich in dissolved metals and other non-volatile elements may be a potential precursor to ore-forming solutions.