The death of an accretion zone as evidenced by the magmatic history of the Sumail ophiolite (Oman)
The death of an accretion zone as evidenced by the magmatic history of the Sumail ophiolite (Oman)
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DOI：
10.1016/0040-1951(88)90248-x
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发表时间：
1988-09
期刊：
影响因子：
2.9
通讯作者：
M. Ernewein;C. Pflumio;H. Whitechurch
中科院分区：
文献类型：
--
作者：
M. Ernewein;C. Pflumio;H. Whitechurch
阿曼北方萨拉希地块蛇绿壳序列显示出复杂的岩浆历史。海洋增生情节导致形成的主要深成序列组成的层状堆晶岩，各向同性辉长岩，席状岩墙复杂和第一拉斑玄武岩熔岩系列（V1）耗尽兼容的元素。第二个岩浆幕紧接着吸积阶段的说明主要是超基性岩侵入体横切主要的深成序列和第二个火山岩套（V2）直接链接，可以看出，从现场证据，更分化的高级侵入岩体。该火山单元包括非常原始的成员，一般以不相容元素的亏损为特征。第三次火山事件（V3）表现出过渡性的轻稀土富集特征。覆盖着蛇绿岩根据野外、矿物学和地球化学资料，提出了苏麦尔蛇绿岩的大地构造演化。在产生了主要蛇绿岩序列的大洋增生阶段之后，上地幔的第二阶段熔融被建议解释第二岩浆幕的成因。这样一个模型很好地解释了V2熔岩的亏损特征。与洋内拆离开始有关的挤压作用使这些第二阶段的熔体从地幔中提取出来，然后进入地壳并部分挤出。V3火山作用晚于蛇绿岩的洋内拆离，但早于其向阿拉伯大陆边缘的仰冲。它被解释为板内沉积型岩浆活动。
The ophiolitic crustal sequence of the Salahi block in the northern part of Oman shows a complex magmatic history. The oceanic accretion episode led to the formation of a main plutonic sequence consisting of layered cumulates, isotropic gabbros, a sheeted dike complex and a first tholeiitic lava series (V1) depleted in compatible elements. The second magmatic episode immediately following the accretion stage is illustrated by predominantly ultrabasic intrusions crosscutting the main plutonic sequence and by a second volcanic suite (V2) directly linked, as can be seen from field evidence, to more differentiated high-level intrusive plutons. This volcanic unit includes very primitive members and is in general characterized by depletion in incompatible elements. A third volcanic event (V3) exhibiting a transitional character enriched in LREE's. caps the ophiolite. These V3 lavas are separated from the V2 unit by a 15 m thick pelagic sedimentary section.A geotectonic evolution of the Sumail ophiolite is proposed on the basis of field, mineralogical and geochemical data. After the oceanic accretion phase that gave birth to the main ophiolitic sequence, a second-stage melting of the upper mantle is suggested to explain the genesis of the second magmatic episode. Such a model accounts well for the depleted character of the V2 lavas. The compression linked to the beginning of the intra oceanic detachment allows the extraction from the mantle of these second-stage melts which are then emplaced in the crust and partly extruded. The V3 volcanism postdates the intraoceanic detachment of the ophiolite, but precedes its obduction onto the Arabian continental margin. It is interpreted as an intraplate seamount-type magmatism.