New evidences of hydrothermal fluids circulation at the Devonian Kess Kess mounds, Hamar Laghdad (eastern Anti‐Atlas, Morocco)

Abstract

International audienc

Differentiating marine vs hydrothermal processes in Devonian carbonatemounds using rare earth elements (Kess Kess mounds, Anti-Atlas, Morocco)

“…3D and 4G). This facies, described for the first time by Franchi et al (2014), has probably been generated by meteoric alteration during subaerial exposure of the Hamar Laghdad succession. One sample (sample 20; Table 1) was collected from the uppermost strata of SRG.…”

“…These deposits are dominated by globular and spongy masses of primary blackish-brown goethite and have been inferred to correspond to fossil vents (Franchi et al, 2014). The ironstone (sample 12; Table 1) is hosted within Fe-rich carbonate cemented by zoned, euhedral dolomite locally breached by veins filled with quartz (sample 11; Table 1).…”

“…Sampling sites for this study were carefully selected on the basis of previous field studies and petrographic and mineralogical data (Cavalazzi et al, 2007;Franchi et al, 2014). Samples for this work were collected from different facies of the SRG corresponding to different depositional settings (Figs.…”

“…Chemical Geology 409 (2015) [69][70][71][72][73][74][75][76][77][78][79][80][81][82][83][84][85][86] The Early Devonian (Emsian) Kess Kess mounds are well exposed at the Hamar Laghdad Ridge in the Tafilalt region (Eastern Anti-Atlas, Morocco;. A hydrothermal origin, based on temperature estimates from fluid inclusions, REE composition, and oxygen isotopic composition of carbonates, and the presence of putative thermophilic faunas was proposed to explain the formation of these micritic mounds (Bełka, 1998;Mounji et al, 1998;Aitken et al, 2002;Berkowski, 2004Berkowski, , 2006Berkowski, , 2008Bełka and Berkowski, 2005;Olempska and Bełka, 2010;Berkowski and Klug, 2012;Jakubowicz et al, 2013;Franchi et al, 2014). Warm fluids (31-56°C, Mounji et al, 1998;40-45°C Franchi et al, 2014) were probably derived from low-temperature hydrothermal activity driven by late-stage magmatic activity related to Early Devonian submarine calc-alkaline volcanism.…”

“…However, the hydrothermal origin of the Kess Kess mounds is still debated because the oxygen isotopic composition (δ 18 O values as low as −11‰ PDB; Franchi et al, 2014) of the Early Devonian limestones is inconclusive and considered inconsistent with unambiguous hydrothermal genesis and probably due to incipient burial diagenesis (Joachimski et al, 1999;Klug et al, 2009).…”