Pétrographie et altération de la matière organiquedu gisement de plomb–zinc–cuivre de tourist–Bou Beker,Maroc nord oriental

Abstract

Reflectance measurements and organic petrography were used to study altered organic matter in the dolomitic Middle Jurassic Beddiane sequence hosting the Beddiane lead–zinc deposit. Organic matter occurs in the lower dolostone units of the formation where zinc sulfide mineralization prevails. The upper units, where lead sulfide mineralization is dominant, contain lesser amounts of organic matter. The organic matter in the Beddiane sequence consists of macerals, amorphous kerogen, and solid bitumen, inertinite and vitrinite are ubiquitous. The amount of exinite increases toward mineralized areas but the ratio exinite/kerogen remains constant. Two types of vitrinite are considered on the basis of their reflectance: Vt1 with low reflectance values (0.3–0.5%) and Vt2 with higher values (0.7–1.25%). The ratio Vt1/Vt2 increases and the reflectance values for Vt1 decrease toward the zinc-prevailing units, Organic matter associated with the mineralization exhibits features such as oxidation halos and desiccation cracks, together with a low-fluorescent exinite. The association of the kerogen content, the trend in reflectance values, and the alteration features of the Mississippi Valley-type Beddiane deposit support the hypothesis that the regional flow of hot brines associated with the mineralization process was the cause of anomalous heating, that the occurrence of exinite maceral and its associated gas played a role in the ore deposition, and that the new chemical equilibrium reached by the zinc-dominant host rock after ore deposition is responsible for the suppressed reflectance values within and near the ore deposits.

Geology, Geochemistry, and Current Genetic Models for Major Mississippi Valley-Type Pb–Zn Deposits of Morocco

“…The geology of the Touissit-Bou Beker district has been well described by numerous investigations (Voirin 1965;Samson 1973;Touahri 1991;Rajlich 1983;Dupuy and Touray;Makhoukhi 1993;Bouabdellah 1994;Torbi and Gélard 1994;Ajaji et al 1998;Aboutahir 1999;Bouabdellah et al 1996aBouabdellah et al , b, 1999Bouabdellah et al , 2001Bouabdellah et al , 2012Bouabdellah et al , 2015. Only a summary of the main conclusions relevant to the present study are given below.…”

“…Two major stages have been distinguished based on petrographic, sedimentological, and isotopic (C, O, Sr) data (Bouabdellah 1994;Aboutahir 1999;Bouabdellah et al 2012). Specifically, these are (1) regionally extensive, pre-ore diagenetic replacement dolomitization that forms 70 vol.% of the dolostone; and (2) epigenetic, ore-related, vug-and fracture-filling saddle dolomite cement.…”

“…Hundreds of carbon and oxygen isotope analyses were performed on several generations of replacement dolostones and ore-related hydrothermal dolomite cements (Bouabdellah 1994;Aboutahir 1999;Bouabdellah et al 2012). Calculated δ…”

“…However, in spite of abundant available geological, mineralogical, and geochemical data (Rajlich 1983;Dupuy and Touray 1986;Makhoukhi 1993;Bouabdellah 1994;Bouabdellah et al 2012Bouabdellah et al , 2015, the basic questions of genesis remain controversial with proposed models ranging from syngenetic to epigenetic. The lack of minerals suitable for radiometric age dating, together with the omnipresence of post-ore oxidizing events, have left the age of Pb-Zn mineralization as the subject of ongoing debate, and therefore any robust genetic model open to controversy.…”

Geochemistry of the sediment-hosted disseminated gold deposits in Southwestern Guizhou Province, China /

“…(1) bio-and abio-degradation (thermal maturation) of organic matter; (2) interaction between the mineralizing hydrothermal solutions, and the pre-existing degraded hydrocarbons and H2S reservoir; (3) interaction between ore-forming fluids, hydrocarbons 184 and H2S produced in the thermal maturation caused by the heating of hydrothermal system; and (4) the biodégradation of organic matters induced by circulating meteoric waters (Bouabdellah et al,1996;Dixon and Davidson, 1996;McGoldrick et al, 1996;Tritlla and Gardellach, 1997;Zentilli et al, 1997). Geological and geochemical evidence show that the ore deposition of SHDG and other strata-bound base metal deposits occurs under reducing environments.…”