The metacherts of the Asima Window, in northeastern U.A.E. at the southeastern corner of the Arabian Peninsula, are the dominant metamorphic sole lithologies of the Semail ophiolite that was obducted onto the Arabian continental margin at the end of the Cretaceous. There have been no previous geochemical studies of these metacherts. The Asima metachert samples of this study form four groups based on geochemistry, petrography and field association: (1) black hematitic, (2) green epidote-chlorite rich, (3) pink piedmontite-bearing and (4) grey micaceous metacherts. A continental margin setting for the parent cherts is indicated geochemically by Al₂O₃ to Fe₂O₃ and SiO₂ ratios, low ΣREE, low La, moderate positive Ce/Ce* and La_n/Ce_n ~ 1. A significant terrigenous fraction was composed of illite, chlorite and Fe hydroxides. A hydrothermal component can be recognized in all of the metachert groups but is particularly evident in the black and green metacherts by low Al/(Al + Fe + Mn), high (Fe + Mn)/Ti, high Ba and Ba/Sr ratios, positive Eu/Eu* and left-leaning REE profiles. Most silica was biogenic. A hydrogenous component included REE’s, Cu, Ni, Zn, V, Ba and Co that were adsorbed onto clays, Fe hydroxide and Mn oxide particles. The Asima cherts were deposited in a marine basin adjacent to but separated from the continental margin by seamounts of the Al Hala Volcanics. These volcanics provided Fe,Mn-rich hydrothermal fluids that mixed with the oxygenated seawaters, leading to rapid hematite deposition (black metacherts) and slow Mn oxidation to form Mn oxide particles that accumulated in the pink metacherts. Grey metacherts were deposited farther from the vents. Green metacherts have similarities to the hydrothermal black metacherts.

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中文翻译：

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与大陆边缘火山海山热液活动有关的阶cher的地球化学：阿联酋的变质底岩

位于阿拉伯联合酋长国东北角阿联酋东北角的Asima窗的变质岩，是Semail蛇绿岩的主要变质唯一岩性，在白垩纪末期被带到阿拉伯大陆边缘。以前没有关于这些微cher石的地球化学研究。根据地球化学，岩相学和田间研究的关系，本研究的阿西玛（Asima）微cher样品分为四类：（1）黑半闪岩，（2）富含绿附子的绿泥石，（3）粉云母和（4）灰色云母微cher。Al ₂ O ₃到Fe ₂ O ₃和SiO _2的地球化学特征表明了母石的大陆边缘设置比率，低ΣREE，低La，中度正Ce / Ce *和La _n / Ce _n〜1.大量的陆源部分由伊利石，亚氯酸盐和氢氧化铁组成。水热组分可以在所有微cher组中识别，但在黑色和绿色微cher中尤为明显，因为低的Al /（Al + Fe + Mn），高的（Fe + Mn）/ Ti，高的Ba和Ba / Sr比，正Eu / Eu *和左倾REE轮廓。大多数二氧化硅是生物成因的。含氢成分包括吸附在粘土上的稀土元素，铜，镍，锌，钒，钡和钴，氢氧化铁和氧化锰颗粒。Asima硅质were石沉积在一个海洋盆地中，该盆地与大陆边缘相邻，但被Al Hala火山的海山隔开。这些火山提供了富含铁，锰的热液，并与含氧海水混合，导致快速的赤铁矿沉积（黑meta石）和缓慢的Mn氧化形成形成在粉红色meta石中的Mn氧化物颗粒。灰色的小cher鱼离通风口较远。绿色的温床与水热的黑色温床相似。

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