ORIGINAL PAPER Geochemistry and mineral chemistry of lode gold mineralisation, SE Egypt: implications for ore genesis and exploration Basem A. Zoheir & Mohamed G. Abdel-Fattah & Sameh M. ElAlfy Received: 14 July 2012 / Accepted: 16 October 2012 # Saudi Society for Geosciences 2012 Abstract Orogenic, lode gold mineralisation in the South Eastern Desert of Egypt is related to quartz veins spatially and temporally associated with conjugate NW- and NE- trending brittle–ductile shear zones. These structures are assumed to be linked to a regional transpression deforma- tion which occurred late in the tectonic evolution of the area. In the Betam deposit, gold is confined to quartz(±carbonate) veins cutting through tectonised metagabbro and metasedi- mentary rocks in the vicinity of small granite intrusions. The ore bodies contain ubiquitous pyrite and arsenopyrite, in addition to minor disseminated chalcopyrite, pyrrhotite, ga- lena, tetrahedrite and rare gold/electrum. New ore micros- copy and electron microprobe studies indicate that most free-milling Au is intimately associated with the late- paragenetic galena–tetrahedrite–chalcopyrite assemblage. An early Fe–As sulphide assemblage, however, shows mi- nor traces of refractory gold. New mineralogical and geo- chemical data are used to better constrain on possible element dispersions for exploration uses. This study indi- cates that parameters that most consistently define primary dispersion of gold in the mine area include pervasive silic- ification, sericite and carbonate alteration. The trace element data of gold lodes reflect a systematic dispersion of gold and certain base metals. Low-cost, extensive exploration pro- grams may use elevated concentrations of Ag, Sb, Cu and Pb as tracers for Au ore zones in the Betam mine area and surroundings. Keywords Lode gold . Geochemistry . Electron microprobe . Element dispersion . Betam deposit . Egypt Introduction A clear association has been recognised between lode gold deposits and accretionary orogens, where several gold deposits are related to a broadly consistent tectono- magmatic setting within the evolving orogen (e.g. Robert et al. 1997; Hagemann and Brown 2000; Poulsen et al. 2000; Groves et al. 2003; Robert 2004; Goldfarb et al. 2005; Miller et al. 2006; Bierlein et al. 2009; Hronsky et al. 2012). Several important orogenic, lode gold ores occur either within or close to large-scale compressional or trans- pressional structures and crustal discontinuities (e.g. Hodgson 1993; Robert 1996; Phillips et al. 1996; Groves et al. 1998; Sillitoe 2000; Haynes 2002). In the crustal continuum model of Groves (1993), gold-bearing quartz veins form over a broad range of upper to mid-crustal pressures and temperatures (200–650 °C and 1–5 kbar). The formation of orogenic gold deposits over a metamor- phic continuum is, however, argued and the high- temperature end of the crustal continuum model is discarded (Tomkins and Grundy 2009). For deposit formation, the mineralising fluids that are widespread in the crust require a focusing mechanism. Networks of structures and litholog- ical contacts can provide the pathways for a focused fluid flow (e.g. Cox et al. 2001; Hodkiewiczi et al. 2005). Stress- driven fluid flow enforces the hydrothermal fluids to mi- grate and to diffuse away from the large faults to deposi- tional sites along smaller splays (e.g. Cox and Ruming 2004; Bierlein et al. 2006). Consistent geological characteristics of the orogenic gold deposits include deformed and variably metamorphosed host rocks, low sulphide concentrations, carbonate–sericite– B. A. Zoheir (*) Department of Geology, Faculty of Science, Benha University, 13518, Benha, Egypt e-mail: basem.zoheir@gmail.com M. G. Abdel-Fattah : S. M. ElAlfy Nuclear Materials Authority of Egypt, P.O. Box: 530, El-Maadi, Cairo, Egypt Arab J Geosci DOI 10.1007/s12517-012-0727-y