Abstract The Khamal complex is an Ediacaran post-collisional gabbro-anorthosite igneous complex that intruded Tonian and Cryogenian subduction-related island arc and ophiolitic rocks and syn-tectonic granitic rocks. The complex is reminiscent of massif-type anorthosites. It has an elliptical shape and is unmetamorphosed and undeformed. The Khamal complex is differentiated into four lithological units, marginal gabbro, anorthosite, central gabbro and northern gabbro. Anorthosite is the most dominant unit and is surrounded by marginal high-Al (Al2O3 (>16 wt%) gabbro and gabbronorite showing a positive Eu anomaly. Iron-rich gabbroic rocks associated with nelsonite (Fe-Ti-P ore) and magnetite-ilmenite (Fe Ti ore) are exposed in the central portion of the anorthosite. Towards the north, less differentiated massive gabbronorite is exposed, which is characterized by its high Al2O3 contents in addition to the MgO contents. The association between anorthosite and Al Fe mafic melts is recorded in several Proterozoic massif-type anorthosite complexes. The formation of the Khamal gabbro-anorthosite complex was most likely related to the wanning stage of the East African orogeny. After the assembly of the Tonian-Cryogenian island arc terranes, slab break-off and lithospheric delamination induced asthenospheric upwelling and ponding of the mafic melt at the crust-mantle boundary. The resulting mantle-derived or lower crustal melt evolved, which led to the formation of floated plagioclase. Then, the plagioclase-rich diapir ascended to form the anorthosite and high-Al marginal gabbroic rocks. The less differentiated high-Al gabbronorite of the northern unit intruding the anorthosite mimics its parental magma but does not directly represent the magma from which anorthosite crystallized. The central gabbroic unit is characterized by an enrichment in iron. This unit might represent the residual melt that was extracted and segregated into a small chamber from the anorthosite, which was emplaced in a dynamic environment. In this chamber the melt underwent further crystal fractionation and accumulation processes. The compositional gap between the nelsonite and magnetite-ilmenite ores and the enclosing gabbroic rocks as well as the similarity between these ores and the host gabbro and the discordant nature of the Fe Ti ore favor the immiscibility origin of the ore.

中文翻译：

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来自阿拉伯地盾的埃迪卡拉纪碰撞后 Khamal 辉长岩-斜长岩复合体及其 Fe-Ti-P 矿石：与元古代地块型斜长岩的类比

摘要 哈马尔杂岩是埃迪卡拉纪后碰撞辉长岩-斜长岩火成岩杂岩，侵入托尼阶和低温纪俯冲相关岛弧、蛇绿岩和同构造花岗岩。该复合体让人联想到地块型斜长岩。它呈椭圆形，未变形、未变形。Khamal 杂岩体分为四个岩性单元，边缘辉长岩、斜长岩、中部辉长岩和北部辉长岩。斜长岩是最主要的单元，被边缘高铝 (Al2O3 (>16 wt%) 辉长岩和辉长岩所包围，显示出正 Eu 异常。富铁辉长岩与菱镁矿（Fe-Ti-P 矿石）和磁铁矿-钛铁矿（Fe Ti 矿石）出露在斜长岩的中部，向北出露差异较小的块状辉长岩，其特点是除了 MgO 含量外，还具有高 Al2O3 含量。在几个元古代地块型斜长岩复合体中记录了斜长岩和铝铁基性熔体之间的联系。Khamal辉长岩-斜长岩复合体的形成很可能与东非造山运动的衰落期有关。在托尼阶-低温岛弧地体组装之后，板块断裂和岩石圈分层导致软流圈上涌和壳幔边界处基性熔体的积水。由此产生的地幔或下地壳熔体演化，导致形成漂浮的斜长石。然后，富含斜长石的底辟上升形成斜长岩和高铝边缘辉长岩。侵入斜长岩的北部单元差异较小的高铝辉长岩模仿其母岩浆，但不直接代表从中结晶出斜长岩的岩浆。中央辉长岩单元的特点是富含铁。该单元可能代表从斜长岩中提取并分离到一个小室中的残余熔体，该室位于动态环境中。在这个室中，熔体经历了进一步的晶体分馏和积累过程。菱镁矿和磁铁矿-钛铁矿与包围的辉长岩之间的成分差异以及这些矿石与主辉长岩之间的相似性和 Fe Ti 矿石的不协调性质有利于矿石的不混溶成因。