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The phosphorite -organic-rich marl -diatom-bearing porcelanite facies association in the 36 Gafsa-Metlaoui Basin represents the classic coastal upwelling trinity. Modified Tethyan 37 waters occurred within the Basin during phosphorite deposition, with decreasing marine 38 productivity from NW to SE evidenced by systematically falling enrichment factors for Cu, 39Ni, Cd and Zn in the phosphorites. Productivity declined in concert with increasing basin 40 isolation during the deposition of the commercial phosphorite beds in the latest Paleocene to 41 earliest Eocene. This isolation trend was temporarily reversed during an episode of maximum 42 flooding associated with the earliest Eocene Paleocene-Eocene Thermal Maximum (PETM). 43

The Bou Jaber Ba-F-Pb-Zn deposit is located at the edge of a Triassic salt diapir in the Salt Diapir Cenomanian. The limestone host rock is hydrothermally altered to ankerite proximal to and within the ore 6 bodies. Quartz as fine-grained bipyramidal crystal formed during hydrothermal alteration of the host rocks. 7The ore mineral assemblage is composed of barite, fluorite, sphalerite and galena in decreasing abundance. 8The ore zones outline distinct depositional events: sphalerite-galena, barite+ankerite and fluorite. Fluid 9 inclusions, commonly oil-rich, have distinct fluids salinities and homogenization temperatures for each of 10 these events: sphalerite-galena (17 to 24 wt% NaCl eq., and Th from 112° to 136°C; ankerite+ barite (11 to 11 17 wt% NaCl eq., and Th from 100° to 130°C); fluorite (19 to 21 wt% NaCl eq., Th from 140° to 165°C). 12The mean temperatures of the ore fluids in the events decreased from sphalerite (125°C) to barite (115°C) and 46

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