Structural Control on Banded Iron Formation (BIF) and Gold Mineralization at Abu Marawat Area, Central Eastern Desert, Egypt

Abstract

Abu Marawat area is considered as a promising site for exploration of gold mineralization, where many ancient gold mines, hydrothermal alteration zones, and intervening quartz veins are present. This study is a field-based structural analysis that aims at revealing the relationship between mineral occurrences and local structural setting. The area is a part of a back-arc volcanosedimentary sequence associated with banded iron formation (BIF) that has undergone extensive ductile and brittle deformation history. This multiple deformation is manifested by four phases. D1 and D2 are the product of compressional stresses and are expressed by F1, F2 and F3 folds in low-grade regionally metamorphosed rocks. D1 was a progressive deformational phase started with F1 folds, which in a later stage were overprinted by F2 folds. It resulted from NW-SE-oriented pure shear and is associated with imbricate thrust stacks, which control the locations of listwanite bearing gold. NE-SW-oriented compressive stress during D2 is displayed by F3-slip folds at the early stage followed by N-S- to NW-trending dip-slip normal faults and related shear zones. Mineralized quartz veins (MQV) were developed post-D2 and pre-D3. Folding and refolding in addition to thrust movement play a significant role in shortening and thickening of the iron formation bands located at the summit of Gebel Abu Marawat. D3 and D4 are expressed by brittle deformation. D3 is displayed by conjugate shear planes represented by sinistral-NW-oriented and dextral-NE–oriented strike-slip faults that led to the dislocation and redistribution of gold mineraliztion associated with both MQV and listwanite. Barren quartz veins trending E-W were also developed along gash fractures formed during this phase of deformation.