GEOLOGY AND MINERALOGY OF MASSIVE SULFIDE ORES FROM THE CENTRAL OKINAWA TROUGH, JAPAN
GEOLOGY AND MINERALOGY OF MASSIVE SULFIDE ORES FROM THE CENTRAL OKINAWA TROUGH, JAPAN
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DOI：
10.2113/gsecongeo.88.8.2210
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发表时间：
1993-12-01
期刊：
影响因子：
--
通讯作者：
PRACEJUS, B
中科院分区：
文献类型：
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作者：
HALBACH, P;PRACEJUS, B
日本冲绳海槽中部的活动喷口和非活动喷口、烟囱以及热液玉石堆中采集了大量硫化物矿石，冲绳海槽是位于太平洋西北部的一个构造活动的陆内弧后盆地。翡翠矿田位于一个被认为受到倾斜剪切带影响的海洋地块段尖端的地点。由此形成的伊泽纳盆地中的小断层提供了从玉石田排出的循环热液的通道。这些流体形成的矿石的化学特征分别为：(1)富锌铅，(2)富巴锌铅，(3)富锌铜，(4)富铁交代，(5)富锌铅侵入长英质火山岩。矿石类型1、2和4来自烟囱，而3种矿石是从土堆中收集的大板条。一些矿石样品显示Au(高达24ppm)和Ag(高达1.1%)的浓度很高。在矿物学和结构上，这些矿石显示出明显的差异，即使总体化学成分是可比的(如1和5)。这些矿石样品在地球化学和矿物学上与黑子型块状硫化矿石有很大的相似之处。然而，玉石矿床的形成尚未完成，处于不成熟阶段。这为研究一种现代的古代矿床提供了独特的机会。
Massive sulfide ores were collected from active and inactive vents and smokers and from mounds of the hydrothermal jade field in the central Okinawa trough (Japan), which is a tectonically active intracontinental back-arc basin located in the northwestern Pacific. The Jade field occurs at a site where the tip of a marine graben segment is thought to be influenced by an obliquely striking shear zone. Small faults in the resulting Izena basin present the paths for circulating hydrothermal solutions discharged at the Jade field. The ores forming from these fluids can be chemically characterized by their respective major components as follows: (1) Zn-Pb rich, (2) Ba-Zn-Pb rich, (3) Zn-Cu rich, (4) Fe-rich replacements, and (5) Zn-Pb-rich impregnations of felsic volcanics. Ore types 1, 2, and 4 originate from chimneys, whereas 3 was collected as large slabs from mounds. Some ore samples show high concentrations of Au (up to 24 ppm) and Ag (up to 1.1%). Mineralogically and texturally, the ores show distinctive differences, even if the overall chemistry is comparable (such as that for 1 and 5). Strong similarities, both geochemically and mineralogically, are found between these ore samples and kuroko-type massive sulfide ores. However, the formation of the Jade deposit is as yet incomplete and at an immature stage. This presents the unique opportunity to examine a modern analogue of an ancient deposit.