Lithology, Mineralogy, and Origin of Serpentine Muds Recovered from Conical and Torishima Forearc Seamounts: Results of Leg 125 Drilling
Lithology, Mineralogy, and Origin of Serpentine Muds Recovered from Conical and Torishima Forearc Seamounts: Results of Leg 125 Drilling
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从圆锥形和鸟岛弧前海山回收的蛇纹石泥的岩性、矿物学和起源：125 段钻探的结果
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发表时间：
1992
期刊：
影响因子：
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通讯作者：
M. Mottl
中科院分区：
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作者：
P. Fryer;M. Mottl
大型蛇纹岩海山常见于海沟轴与马里亚纳和伊扎-波宁海内弧的活火山锋之间的弧前地区。显然，海山既可以形成泥火山，由夹带变质超镁铁质和基性岩的松散蛇纹岩泥流组成，也可以形成由蛇纹岩化超镁铁质部分覆盖松散蛇纹岩滑塌沉积物和泥流的基底块体，可能是底顶侵位。从马里亚纳前弧地区圆锥海山的三个地点和伊豆-波宁前弧地区鸟岛海山的两个地点发现的粘土和粉砂大小的蛇纹石主要由温石棉、水镁石、绿泥石和粘土组成。各种辅助矿物证明在一些样品中存在不寻常的孔隙流体。文石，在蛇纹岩矿床钻探的深度不稳定，存在于圆锥海山的许多表层岩心中。蛇辉石矿物通常是蛇纹石与地下水相互作用的风化产物，在大多数样品中都有发现。文石和碳酸盐氢氧化物矿物的存在表明蛇纹岩矿床与海水以外的流体相互作用。陆地上暴露的沉积蛇纹岩矿床与ODP Leg 125上钻探的蛇纹岩海山中发现的矿床非常相似。我们认为锥状海山可能是研究这些沉积蛇纹岩体原位形成的一个典型地点。此外，我们认为锥状海山和鸟岛前弧海山的沉积都表明，通过蛇纹岩与海水和俯冲相关流体的相互作用，蛇纹岩化可以在海山内部继续进行。
Large serpentinite seamounts are common in the forearc regions between the trench axis and the active volcanic fronts of the Mariana and Izu-Bonin intraoceanic arcs. The seamounts apparently form both as mud volcanoes, composed of unconsolidated serpentine mud flows that have entrained metamorphosed ultramafic and mafic rocks, and as horst blocks, possibly diapirically emplaced, of serpentinized ultramafics partially draped with unconsolidated serpentine slump deposits and mud flows. The clayand silt-sized serpentine recovered from three sites on Conical Seamount on the Mariana forearc region and from two sites on Torishima Forearc Seamount on the Izu-Bonin forearc region is composed predominantly of chrysotile, brucite, chlorite, and clays. A variety of accessory minerals attest to the presence of unusual pore fluids in some of the samples. Aragonite, unstable at the depths at which the serpentine deposits were drilled, is present in many of the surficial cores from Conical Seamount. Sjogrenite minerals, commonly found as weathering products of serpentine resulting from interaction with groundwater, are found in most of the samples. The presence of aragonite and carbonate-hydroxide hydrate minerals argues for interaction of the serpentine deposits with fluids other than seawater. There are numerous examples of sedimentary serpentinite deposits exposed on land that are very similar to the deposits recovered from the serpentine seamounts drilled on ODP Leg 125. We suggest that Conical Seamount may be a type locality for the study of in situ formation of many of these sedimentary serpentinite bodies. Further, we suggest that both the deposits drilled on Conical Seamount and on Torishima Forearc Seamount demonstrate that serpentinization can continue in situ within the seamounts through interaction of the serpentine deposits with both seawater and subduction-related fluids.