Glassy and Basaltic Fragments within Graded Volcaniclastic Sediments, East Mariana Basin, Deep Sea Drilling Project Leg 89
Glassy and Basaltic Fragments within Graded Volcaniclastic Sediments, East Mariana Basin, Deep Sea Drilling Project Leg 89
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东马里亚纳盆地深海钻探项目第 89 段分级火山碎屑沉积物中的玻璃质和玄武岩碎片
DOI：
10.2973/dsdp.proc.89.114.1986
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发表时间：
1986
期刊：
影响因子：
--
通讯作者：
P. Floyd
中科院分区：
文献类型：
--
作者：
P. Floyd
在585站的基底剖面中，浊流沉积的分级火山碎屑沉积物是混合的玻璃-岩屑凝灰岩和火山岩，含有少量的斜长石和单斜辉石晶体碎片。它们代表了在近露出的海山的侧面和顶部发育的玄武质玻璃碎屑岩堆积物的改造产物。它们随后被浊流带着少量的礁石碎片沿着卷入马里亚纳盆地南部的深海深处。玻璃质碎屑中的囊泡平均非常小（直径为0.1-0.2 mm），尽管它们的体积（作为封闭玻璃的百分比）相对较高，表明初始熔岩侵入的最大深度< 400 m。浅水环境的透明碎屑岩是由通常相关的浅水动物碎屑和ooids。没有明显的证据表明与玻璃碎屑岩有关的火山碎屑或火山碎屑物质。玻璃，很少保存为铁锰矿，通常被钾长石或蒙皂石取代，范围从高度泡状斑状到中度泡状斑状类型，具有橄榄石，斜长石和单斜辉石微斑晶和巨斑晶的各种组合。岩屑碎屑具有一系列的结构，从不透明的淬火结构的玄武玻璃到次晶和全晶玄武岩，通常为斜长石或斜长石-单斜辉石-斑状。玻璃质和岩屑碎屑和纹理之间的主要岩相学特征的相关性，根据冷却历史，允许识别五个“熔岩类型”，其中每一个都代表一个喷出的插曲。所有的火山碎屑岩都普遍蚀变，发育有斜长岩、各种颜色的蒙皂石、绿鳞岩和典型的低沸石相的沸石。蚀变可分为两个阶段：最初破碎后的海底蚀变，以及随后在迁移到深海深处后的埋藏过程中的蚀变。
Graded volcaniclastic sediments deposited by turbidity currents in the basal section at Site 585 are mixed vitric-lithic tuffs and lapilli-stones with minor Plagioclase and clinopyroxene crystal fragments. They represent the reworked products of basaltic hyaloclastite accumulations that developed on the flanks and tops of nearly emergent seamounts. They were subsequently swept to the abyssal depths of the southern Mariana Basin by turbitity currents, along with minor reef debris. Vesicles in glassy clasts are on average very small (0.1-0.2 mm diameter), although their volumes, as a percentage of the enclosing glass, are relatively high and suggest a maximum depth of initial lava intrusion of < 400 m. A shallow-water environment for the hyaloclastites is indicated by the commonly associated shallow-water faunal debris and ooids. There is no clear evidence of epiclastic or pyroclastic material associated with the hyaloclastites. Glass, rarely preserved as sideromelane, is generally replaced by palagonite or smectites, and ranges from highly vesicular aphyric to moderately vesicular phyric types, with various assemblages of olivine, Plagioclase, and clinopyroxene microphenocrysts and megaphenocrysts. Lithic clasts exhibit a range of textures—from opaque quench-textured tachylite glass to hypocrystalline and holocrystalline basalts—which are commonly Plagioclaseor plagioclase-clinopyroxene-phyric. Correlation of primary petrographic features between vitric and lithic clasts and textures, based on cooling history, allows the identification of five "lava types," each of which represents an extrusive episode. All the volcaniclastics are pervasively altered, with the development of palagonite, various colored smectites, celadonite, and zeolites typical of the lower zeolite facies. Two phases of alteration are recognized: submarine alteration after initial fragmentation, and subsequent alteration during burial after transportation to abyssal depths.