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首页> 外文会议> >A first extensive hydrothermal field associated with Kuroko-type deposit in a Silicic Submarine caldera in a Nascent Rift Zone, Izu-Ogasawara (Bonin) arc, Japan
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A first extensive hydrothermal field associated with Kuroko-type deposit in a Silicic Submarine caldera in a Nascent Rift Zone, Izu-Ogasawara (Bonin) arc, Japan

机译：日本伊豆小gas原（波宁）弧新生裂谷硅质海底破火山口中与黑子型沉积有关的第一个广阔的热液场

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A huge hydrothermal field of 500 by 700 m across associated with a modern analogue of Kuroko-type deposit was first found in the Bayonnaise knoll caldera in a nascent rift zone westward the volcanic front of the Izu-Ogasawara (Bonin) island arc, Japan during the April 2003 Hakurei-maru No.2 cruise since two major Kuroko-type deposits had been reported on the volcanic front. The dacite knoll caldera associated with a post-caldera dome has the slightly ellipsoidal caldera rim of 3 by 2.5 km wide with about 200 m relief, and its floor is about 840-920 m below sea level. The hydrothermal field, which occurs between water depths of about 800 m and 700 m around the southeastern caldera floor, exists near the intersection of caldera boundary fault and an inferred N-S trending normal fault in a back-arc rift zone. In the field many sulfide chimneys with different sizes less than 10 m high on sulfide mounds are distributed on the marginal area between the caldera floor and sloping talus deposits at the foot of the caldera wall, and are buried in part by talus composed of pumice and dacite fragments and their breakdown materials. They are still active and some of them are oxidized to reddish materials. Sulfide chimneys recovered by finder-installed power grab are mainly composed of sphalerite associated with chalcopyrite, galena, pyrite and barite, and chemically enriched in Au up to 14 ppm and Ag up to 1400 ppm with major Zn, moderate Ba, and minor Pb, Hg and Fe. Since the caldera is located exactly near the intersection of the caldera boundary fault and the N-S back-arc rift fault, the ambient area including the caldera is tectonically active and in an extensional field. The finding of Kuroko-type deposit implies that possible areas of Kuroko-type mineralization may still exist in the N-S rift zones along the volcanic front.
机译：在日本伊豆-小gas原（Bonin）岛弧前西面的新生裂谷带的Bayonnaise丘陵破火山口中首次发现了一个宽500×700 m的巨大热液场，与黑子型矿床的现代类似物有关。自2003年4月以来，据报道火山前部有两个主要的黑子类型的沉积物，博多丸2号巡游。与破火山口后穹顶相连的达克特丘陵破火山口的椭圆形破火山口边缘为3乘2.5公里，宽约200 m，其地面在海平面以下约840-920 m。在东南火山口底板周围约800 m至700 m的水深之间发生的热液场，存在于火山口边界断层与推断的N － S趋势正断层的交点附近，该区域位于后弧裂陷区。在田间，许多硫化物丘上的大小小于10 m的硫化物烟囱分布在破火山口底部和破火山口壁下方的距骨沉积物之间的边缘区域，部分被浮石和滑石组成的距骨掩埋。碎片碎片及其击穿材料。它们仍然活跃，其中一些被氧化为微红色物质。通过取景器安装的功率采集器回收的硫化物烟囱主要由闪锌矿与黄铜矿，方铅矿，黄铁矿和重晶石组成，并且化学富集了高达14 ppm的Au和高达1400 ppm的Ag，并具有主要的Zn，中度的Ba和次要的Pb，汞和铁。由于破火山口恰好位于破火山口边界断层与N-S后弧裂谷断层的交点附近，因此包括破火山口在内的周围区域在构造上是活跃的，并且处于扩展场中。黑子型矿床的发现暗示着黑子型矿化的可能区域可能仍存在于火山前缘的南北裂谷带中。

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