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首页> 外文期刊>Journal of Asian earth sciences >Petrology of the dykes from the Waziristan Ophiolite, NW Pakistan
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Petrology of the dykes from the Waziristan Ophiolite, NW Pakistan

机译：巴基斯坦西北瓦兹里坦蛇绿岩的岩相岩石学

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摘要

The Waziristan Ophiolite is located in the suture zone between the Indian Plate to the east and Afghan Block to the west. It is highly dismembered and divisible into three main sheets or nappes, which from east to west are: the Vezhda Sar Nappe, entirely comprised of pillow basalts; the Boya Nappe, made up of ophiolitic melange with an intact section in its basal part; and the Datta Khel Nappe, consisting mainly of sheeted dykes with smaller proportions of other components. Faunal evidence suggests that the ophiolite is of Tithonian-Valanginian age. It was thrust over the Mesozoic shelf-slope sediments of the Indian Plate to the east during the Paleocene and is uncon-formably overlain by sedimentary rocks of Early to Middle Eocene age to the west. Beside the sheeted dykes, best exposed in the hanging wall of the Datta Khel Thrust ENE of Datta Khel, the ophiolite also contains isolated dykes. These are doleritic and basaltic in composition. The dykes contain high Na_2O contents and high FeO~t/MgO and LILE/HFSE ratios, and low TiO_2 (< 0.1 wt%) and K_2O contents. Non-depletion of Nb and high LILE/HFSE ratio negate, respectively, an island-arc or mid-ocean ridge setting for these dykes. Enrichment in the LILE suggests the involvement of a crustal component driven by fluids along the subduction zone. Several geochemical parameters suggest that the dykes of Waziristan Ophiolite have transitional characteristics between mid-ocean ridge basalt and island-arc tholeiite. It is therefore proposed that these dykes may have originated in a back-arc basin tectonic setting.
机译：瓦济里斯坦蛇绿岩位于东印度板块与西阿富汗块之间的缝合带。它高度易碎，可分为三个主要的床单或尿布，从东到西依次为：Vezhda Sar Nappe，完全由枕形玄武岩组成；博雅纳普犬（Boya Nappe）由乳脂状混杂物组成，基部完整。达塔·凯尔纳普（Datta Khel Nappe）主要由片状堤坝组成，其他成分所占比例较小。有趣的证据表明，蛇绿岩是铁通-瓦朗吉尼时代。在古新世时期，它被推覆到印度板块的中生代陆架斜坡沉积物上，并被西部早至中新世时期的沉积岩非整合地覆盖。除了片状堤坝外，蛇绿岩还含有孤立的堤坝，最好是暴露在Datta Khel的Datta Khel Thrust ENE的悬挂壁上。这些成分在成分上是钙质的和玄武质的。堤坝含有较高的Na_2O含量，较高的FeO〜t / MgO和LILE / HFSE比，以及较低的TiO_2（<0.1 wt％）和K_2O含量。 Nb的不耗尽和高LILE / HFSE比分别抵消了这些堤坝的岛弧或中洋脊环境。 LILE中的富集表明受俯冲带流体驱动的地壳成分的参与。几个地球化学参数表明，瓦济里斯坦蛇绿岩的堤坝在中海脊玄武岩和岛弧辉绿岩之间具有过渡特征。因此，建议这些堤坝可能起源于弧后盆地的构造环境。

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