Y-015. Hypertensive disorders of pregnancy and alterations in brain metabolites in preterm infants: a multi-voxel proton MR spectroscopy study

Abstract

Understanding the genetic mechanism of calcite cement can facilitate the prediction of its distribution, which can improve the accuracy of reservoir quality prediction, however, the growth mechanisms of calcite cement still is not a totally resolved problem. This study reported the results of petrographic, cathodoluminescence, and in-situ major and rare earth elements found in a buried shallow marine sandstone (Donghe sandstones), located in Tarim Basin, NW China. Calcite cements were found as blocky and poililotopic and occluded pores, precipitated in an open marine environment, showed dominantly dull-luminescence with partially dark-red luminescence, during which they precipitated from the dissolution of bioclastic grains and bacterial sulfate reduction (BSR). These were accompanied by the dissolution of Mn- and Fe-oxides/oxyhydroxides, the reduced Fe2+ precipitating as pyrites, and the reduced Mn2+ being incorporated into the lattice of the precipitating calcite cements, which resulted in precipitated calcite cements showing dark-red luminescence under cathodoluminescence images. During shallow buried, BSR were occurred because of water washing of accumulated hydrocarbon reservoirs, which dissolve the early precipitated calcite cements, and subsequently precipitated at the location where the decrease inpCO2 was associated with increasing permeability. Meanwhile, the reduced Mn2+ and Fe2+ that originated from the dissolution of Mn- and Fe-oxides/oxyhydroxides were incorporated into the lattice of calcite cements and precipitated as pyrites, respectively, resulting in the calcite cements showing orange-red and orange-yellow luminescence with a low and high content of Mn and Fe, respectively. Calcite cements precipitated during deep burial, which were characterized by significantly high contents of Fe, Mn, K, Si, and replaced quartz grains, during which precipitation the messenger film water that covered the surface of clastic grains as the mediation for diagenesis reactions. Based on these results, the model of genetic mechanism and diagenetic evolution path is established for shallow marine sandstone, which provides insights into the burial diagenesis processes of calcite cements in marine sandstone.