MICROSTRUCTURAL FEATURES OF A SUBAQUEOUS LAVA FROM BASALTIC CRUST OFF THE EAST PACIFIC RISE (ODP SITE 1256 , COCOS PLATE)
MICROSTRUCTURAL FEATURES OF A SUBAQUEOUS LAVA FROM BASALTIC CRUST OFF THE EAST PACIFIC RISE (ODP SITE 1256 , COCOS PLATE)
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东太平洋隆起玄武岩地壳水下熔岩的微观结构特征（ODP 站点 1256，COCOS 板块）
DOI：
10.4454/ofioliti.v31i2.334
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发表时间：
2006
期刊：
影响因子：
1.3
通讯作者：
S. Umino
中科院分区：
文献类型：
--
作者：
L. Crispini;P. Tartarotti;S. Umino
这项工作检查了大量的玄武岩熔岩侵位在水下环境和钻探ODP网站1256。1256号站点在ODP第206航次（6° 44 N，91° 56 W;危地马拉盆地）期间在东太平洋海隆的东侧钻探，位于15 Ma前的海洋地壳中，由超快速海底扩张（约100 Ma）形成。220毫米/年）。块状熔岩位于薄层流和帽枕状熔岩之间，薄层流中有少量的透明碎屑岩、角砾岩和岩脉。在1256 C和1256 D两个相距30 m的孔中发现了块状玄武岩，1256 C孔的厚度为35 m，1256 D孔的厚度为75 m。它可以被解释为一种积水熔岩，起源于在陡峭的古地形的轴外>3-5 km凹陷中积累的快速喷发的熔岩（Teagle等人，2004年）。
1256孔熔岩池被划分为不同的岩石学单元和构造单元。识别出五个主要构造单元，具有不同的关键流动相关结构和同岩浆或晚期岩浆构造。韧性和脆-韧性结构归因于流动给约束的熔岩的侵位机制和可能的海底地形。不寻常的纹理特征有关的流动运动学被认为主要是在顶部和底部的熔岩池，而脆韧性和脆性变形发生在整个积水体。在基地的显微结构可以解释为流动有关的变形热韧性聚结飞溅碎屑爆发在侵位的第一阶段。或者，它们可能是在最后的侵位阶段熔岩回流期间形成的。
This work examines a massive basaltic lava emplaced in a subaqueous environment and drilled at ODP Site 1256. Site 1256 was drilled on the eastern flank of the East Pacific Rise during ODP Leg 206 (6°44N, 91°56W; Guatemala Basin), located in 15 Ma old oceanic crust created by superfast seafloor spreading (ca. 220 mm/yr). The massive lava lies between thin sheet flows and caps pillow lavas, sheet flows with minor hyaloclastite, breccia and dikes. The massive basalt was encountered in two holes, 1256C and 1256D, which are 30 m apart, and has a thickness of 35 m in Hole 1256C and 75 m in Hole 1256D. It can be interpreted as a ponded lava, originated by rapidly erupted lava accumulated in a off axis >3-5 km depression of a steep paleotopography (Teagle et al., 2004).
The Hole 1256 lava pond has been divided into distinct petrographic units and structural units. Five main structural units with different key flow-related textures and syn-magmatic or late magmatic structures were recognized. Ductile and brittle-ductile structures attributed to the flow gives constraints about the emplacement mechanism of the lava and possibly seafloor topography. Unusual textural features related to the flow kinematics were recognized mainly in the top and in the bottom parts of the lava pond, whereas brittle-ductile and brittle deformations occur throughout the whole ponded body. Microstructures in the base may be interpreted as flow-related deformation of hot ductile coalesced spatter clasts erupted during the first stages of emplacement. Alternatively, they may have been formed during lava drain-back, in the final emplacement stages.