Reworking of intra-oceanic rocks in a deep sea basin: example from the Bou-Maiza complex (Edough massif, eastern Algeria)

Metagabbros and amphibolites exposed in the Bou-Maïza area of the Edough massif (northeast Algeria) are described in detail. Field and petro-structural observations point to the syn-sedimentary emplacement of gabbros as clasts, blocks and lenses of polymictic gabbroic breccias. Associated amphibolites display fine-scale parallel sedimentary bedding and represent mafic epiclastites, litharenites and mafic greywackes. The mafic beds and lenses are intercalated with aluminous pelitic schists of continental origin, quartzite and marble. It is concluded that all mafic rocks from this locality derive from the erosion of an oceanic plutono-volcanic complex of MORB affinity that was reworked in a block matrix mélange and emplaced as turbidites and debris flows during the Mesozoic. We propose a convergent plate margin setting for these formations connected with the subducted Calabrian branch of the Tethyan slab.

对阿尔及利亚东北部埃多夫地块布迈扎（Bou-Maïza）地区出露的变辉长岩（Metagabbros）与角闪岩（amphibolites）开展了详细描述。野外与岩石构造观测结果显示，辉长岩以复成分辉长岩角砾岩的岩屑、块体及透镜体形式完成同沉积就位。伴生的角闪岩发育微细平行沉积层理，归属于镁铁质碎屑岩、岩屑石英砂岩及镁铁质杂砂岩。镁铁质岩层与透镜体与陆源成因的富铝泥质片岩、石英岩及大理岩呈互层产出。研究得出结论：该区域所有镁铁质岩石均来自具有洋中脊玄武岩（MORB）亲缘性的洋壳深成-火山杂岩体的剥蚀产物，该杂岩体曾在块基质混杂岩中遭受改造，并于中生代以浊积岩与碎屑流的方式就位。我们提出，上述地层形成于与特提斯俯冲板片卡拉布里亚分支相关的汇聚板块边缘构造背景。