Influence of Climate and Tectonics on the Crystallization of Carnallite and Related Salts in the Congolese Atlantic Basin during the Lower Cretaceous, Republic of Congo  

作　　者：Daphne Steimer Garcia Nkokani Milandou Hilaire Elenga Maurice Dieudonné Malounguila Nganga Mathurin Enama Mengong Daphne Steimer Garcia Nkokani Milandou;Hilaire Elenga;Maurice Dieudonné Malounguila Nganga;Mathurin Enama Mengong(Center for Geological and Mining Research, Brazzaville, Republic of Congo;Faculty of Science and Technology, Geology Course, Marien Ngouabi University, Brazzaville, Republic of Congo;Newco Mining SA, Pointe-Noire, Republic of Congo)

机构地区：[1]Center for Geological and Mining Research, Brazzaville, Republic of Congo [2]Faculty of Science and Technology, Geology Course, Marien Ngouabi University, Brazzaville, Republic of Congo [3]Newco Mining SA, Pointe-Noire, Republic of Congo

出　　处：《Open Journal of Geology》2023年第1期51-71,共21页地质学期刊（英文）

摘　　要：Lithological, petrographic, and morphoscopic studies were conducted on cuttings and cores from three boreholes drilled in the Loemé salt, Kanga site, Republic of the Congo, to determine 1) the preferential conditions for crystallization of carnallite and associated salts and 2) to reconstruct paleoenvironmental and paleoclimatic conditions at the time of sedimentation. Sequential analysis of logs, sedimentary structures, carnallitite facies and associated salts concluded to the existence of a potassic carnallitite lagoon basin with low water cover, on a very wide and extensive plateau, affected by coastal waves and swells resulting from successive collapses. This basin evolved in two phases: confined and then open. The regular stratifications of halite, the rhythmicity of the halite-carnallitite elementary sequences are characteristic of salts that precipitated in relatively stable brines. These salts are therefore tectonosedimentary. The brecciated facies of the carnallitites sometimes associated with tachyhydrite result from the evolution of these deposits into salt crusts reworked by the surges into subaquatic allochemical gravelly cords under water. These crusts mark stages of partial and complete drying of the basin in a very hot and arid climate. Prolonged exposure of halite brines as well as their homogenization by surges accelerated evaporation and their abrupt evolution into carnallite brines obstructing the fossilization of sylvite. The precipitation of tachyhydrite marks the final stage of the successive complete drying of the basin.Lithological, petrographic, and morphoscopic studies were conducted on cuttings and cores from three boreholes drilled in the Loemé salt, Kanga site, Republic of the Congo, to determine 1) the preferential conditions for crystallization of carnallite and associated salts and 2) to reconstruct paleoenvironmental and paleoclimatic conditions at the time of sedimentation. Sequential analysis of logs, sedimentary structures, carnallitite facies and associated salts concluded to the existence of a potassic carnallitite lagoon basin with low water cover, on a very wide and extensive plateau, affected by coastal waves and swells resulting from successive collapses. This basin evolved in two phases: confined and then open. The regular stratifications of halite, the rhythmicity of the halite-carnallitite elementary sequences are characteristic of salts that precipitated in relatively stable brines. These salts are therefore tectonosedimentary. The brecciated facies of the carnallitites sometimes associated with tachyhydrite result from the evolution of these deposits into salt crusts reworked by the surges into subaquatic allochemical gravelly cords under water. These crusts mark stages of partial and complete drying of the basin in a very hot and arid climate. Prolonged exposure of halite brines as well as their homogenization by surges accelerated evaporation and their abrupt evolution into carnallite brines obstructing the fossilization of sylvite. The precipitation of tachyhydrite marks the final stage of the successive complete drying of the basin.

关 键 词：Potassium Lagoon SURGES Stable Brines RHYTHMICITY Elementary Sequences Salt Crusts Arid Climate Republic of the Congo 

分 类 号：P61[天文地球—矿床学]