The Khzama ophiolite is a highly dismembered complex located in the Siroua inlier of the Moroccan Anti-Atlas Belt. It consists of ultramafic rocks, cumulate gabbros, sheeted dikes, pillow lavas, and an overlying volcano-sedimentary sequence. Three main tectonic slices of sheeted dike complexes are studied in detail along three rivers, exposing well preserved outcrops where individual dikes are clearly distinguishable from the intruded host rock (Assif n’Tinzla, Assif n’Tasriwine, and Assif n’Iriri). Sheeted dikes of the Khzama ophiolitic complex are basaltic to andesitic in composition, displaying a clear sub-alkaline nature. We identify two sets of dikes that originate from lower High-Ti series (HTS) lavas and overlying upper Low-Ti series (LTS) lava. The immobile trace-element signatures of these rocks point to a genesis on a backarc environment with magmas sourced in a supra-subduction zone (SSZ) at the spinel peridotite zone. The obtained SHRIMP U-Pb data of the gabbro represent the first radiometric age of zircon extracted from the mafic rocks that were intruded by the sheeted dike complex of the Khzama ophiolite. These grains yield a concordia age of 763 ± 5 Ma, which is consistent with the 761.1 + 1.9/−1.6 and 762 + 1/−2 Ma U-Pb zircon ages of plagiogranites of Siroua. Based on their mineralogy, modal proportions, and major element chemistry, the felsic dikes are classified as high silica–low alumina trondhjemites or plagiogranites. These plagiogranites were likely formed by the partial melting of mafic rocks rather than by extreme fractional crystallization. A plagiogranite dated at 777 ± 4.7 Ma (U-Pb on zircon) is significantly older than the ca. 762 Ma plagiogranites previously recorded for the Khzama locality, suggesting a long-lived supra-subduction zone (SSZ) with conditions for the hydrous melting of mafic rocks.

中文翻译：

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新元古代Backarc盆地Khzama蛇绿岩的地球化学和年代学（摩洛哥反阿特拉斯山脉）：构造-法律意义

Khzama蛇绿岩是一个高度肢解的复合体，位于摩洛哥反阿特拉斯山脉西鲁阿内陆地区。它由超镁铁质岩石，累积的辉长岩，​​堤防薄片，枕状熔岩和上覆的火山沉积序列组成。沿着三条河流详细研究了三片主要的片状堤防复合体构造，露出了保存完好的露头，在这里露头的堤防与侵入的主岩（Assif n'Tinzla，Assif n'Tasriwine和Assif n'Iriri）有明显区别。Khzama卵石质复合物的片状堤坝在成分上是玄武岩至安山岩，表现出明显的亚碱性。我们确定了两组堤防，它们来自下部高Ti系列（HTS）熔岩和上部上部Low-Ti系列（LTS）熔岩。这些岩石的不可移动的痕量元素特征指向在弧后环境中的成因，其岩浆起源于尖晶石橄榄岩区的超俯冲带（SSZ）。所获得的辉长岩的SHRIMP U-Pb数据代表从由Khzama蛇绿岩的片状堤复合体侵入的镁铁质岩石中提取的锆石的第一个辐射年龄。这些晶粒产生的共生年龄为763±5 Ma，这与Siroua斜长花岗岩的U-Pb锆石年龄761.1 + 1.9 / -1.6和762 + 1 / -2 Ma一致。根据它们的矿物学，模态比例和主要元素化学，长英堤堰被分类为高硅石-低氧化铝菱锰矿或斜长花岗岩。这些斜长花岗岩可能是由镁铁质岩石的部分熔融而不是极端的分步结晶形成的。777±4.7 Ma的斜长花岗岩（锆石上的U-Pb）比钙长得多。先前在Khzama地区记录了762 Ma斜长花岗岩，表明长寿命超俯冲带（SSZ）具有镁铁质岩石含水熔融的条件。