Fig. 3

Optical microscopy and CL on thin sections. a partial early dolomitization replacing both the micritic matrix, grains and calcite cements observed in polarized non-analyzed light under optical microscopy; b same thin section under CL putting in evidence two types of calcite cement (isopachous IC and blocky calcite BC) as well as the T1-a fine to medium early dolomite; c CL photograph of the T1-b dolomite exhibiting medium rhombs with a dull red luminescence and rare thin zonations. The dark spots represent secondary moldic porosity; d CL Evidence the remaining dolomite TD1 in secondary moldic pore resulting from dolomite dissolution during dedolomitization; e optical microscopy under natural light of the fabric destructive sucrosic dolomite. The rhombs core appears cloudy due to the presence of inclusions while the outer rims appears clear. The yellow to brown areas are intercrystalline pores filled by resin used for thin section manufacturing and f same thin section under CL, the sucrosic dolomite T2 exhibiting thin zonation in the clear rims, evidence for chemical modification during precipitation