Abstract

Clay minerals in Holocene–Pleistocene sediments from Hole 858B DSDP drilled at 20 m from the black smoker in the Dead Dog hydrothermal field, axial valley of the Juan de Fuca Ridge, were scrutinized for the first time by modeling the X-ray diffraction patterns in combination with the splitting of 060 reflection profiles into individual maximums. In the section of the sedimentary cover drilled to a depth of 38.6 mbsf, we can distinguish three sediment groups, with successive transformation of clay minerals reflecting a high temperature gradient. Terrigenous clay minerals (dioctahedral illite, mixed-layer smectite-illite, and trioctahedral chlorite) are preserved in the 1.97–7.2 mbsf interval. Terrigenous illite and chlorite were preserved and trioctahedral mixed-layer chlorite-smectite and corrensite were formed in the 7.2–16.7 mbsf interval. At 16.7–38 mbsf, all terrigenous clay minerals were transformed into a new assemblage of trioctahedral phases: corrensite minerals, mixed-layer talc-smectite, and chlorite. Chlorite alone was found at 38.4 mbsf. Structural transitions of clay minerals imply their formation at each stage by the dissolution and synthesis. Metalliferous sediments in the 0–1.97 mbsf interval comprise a mixture of partially altered terrigenous clay minerals and the indicator Fe-rich dioctahedral mixed-layer mica-smectite, which was formed from a hydrothermal fluid mixed with seawater. The composition of clay minerals in the 11.65–12.60 mbsf interval was transformed by high temperature of the hydrothermal fluid penetrating from the discharge channel of the hydrothermal convective system into the tectonic horizontal fracture of the sedimentary cover in the 10.41–11.65 mbsf interval.

中文翻译：

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Juan de Fuca Ridge 858B 洞热液系统中心沉积物中粘土矿物形成的特殊性

摘要

首次通过模拟 X 射线衍射图案，对 Juan de Fuca 山脊轴向谷 Dead Dog 热液场中距离黑烟囱 20 m 处钻孔 858B DSDP 的全新世-更新世沉积物中的粘土矿物进行了仔细检查。结合将 060 反射轮廓分割成单独的最大值。在钻孔深度为 38.6 mbsf 的沉积盖层剖面中，我们可以区分出三个沉积物组，粘土矿物的连续转变反映了高温梯度。陆源粘土矿物（双八面体伊利石、混层蒙脱石-伊利石和三八面体绿泥石）保存在 1.97-7.2 mbsf 区间。陆源伊利石和绿泥石得以保存，7.2～16.7 mbsf层段形成三八面体绿泥石-蒙脱石和钙镁石混层。16 岁。7-38 mbsf，所有陆源粘土矿物都转变为新的三八面体相组合：钙镁石矿物、混合层滑石蒙脱石和绿泥石。在 38.4 mbsf 处仅发现亚氯酸盐。粘土矿物的结构转变意味着它们在每个阶段通过溶解和合成形成。0-1.97 mbsf 区间的含金属沉积物包括部分蚀变的陆源粘土矿物和指示剂富铁二八面体混合层云母蒙脱石的混合物，该混合物由热液与海水混合形成。11.65~12.60 mbsf 层段粘土矿物的组成被热液从热液对流系统排放通道渗入到10.41~11 层沉积盖层的构造水平裂缝中的高温所转化。