نتایج جستجو برای: diagenetic processes
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Sedimentary rocks at Eagle crater in Meridiani Planum are composed of fine-grained siliciclastic materials derived from weathering of basaltic rocks, sulfate minerals (including magnesium sulfate and jarosite) that constitute several tens of percent of the rock by weight, and hematite. Cross-stratification observed in rock outcrops indicates eolian and aqueous transport. Diagenetic features inc...
Diagenetic theory, as it is often stated, is formally incomplete in the sense that it contains more dependent variables than the number of equations in the theory. Heretofore, this situation has been resolved ordinarily by introducing an empirical equation for porosity, , or equivalently the solid volume fraction, s 1 , as a function of depth. In contrast, the theory of compaction, that is comb...
Early diagenetic sediment-hosted stratiform copper (eSSC) mineralization results from low-temperature cuprous chloride complexes carried by saline aqueous solution circulating through footwall aquifers. Favorable copper solubilities are attained in moderately oxidizing, near-neutral pH solutions. That specific oxidation level is not determined by co-existence with hematite, with its near-indisc...
Phosphatic sedimentary rocks preserve a record of early animal life different from and complementary to that provided by Ediacaran fossils in terminal Proterozoic sandstones and shales. Phosphorites of the Doushantuo Formation, South China, contain eggs, egg cases, and stereoblastulae that document animals of unspecified phylogenetic position; small fossils containing putative spicules may spec...
Isoleucine, one of several amino acids isolated from a suite of welldated deep-sea cores, shows a progressive increase in the degree of racemization with the age of the sediment. Amino acids in sediments show an initial rate of racemization almost an order of magnitude faster than the rate observed for free amino acids at a comparable pH and temperature. The observed kinetics depend on a variet...
Multiple sulphur (S) isotope ratios are powerful proxies to understand the complexity of S biogeochemical cycling through Deep Time. The disappearance of a sulphur mass-independent fractionation (S-MIF) signal in rocks <~2.4 Ga has been used to date a dramatic rise in atmospheric oxygen levels. However, intricacies of the S-cycle before the Great Oxidation Event remain poorly understood. For ex...
Temporal variations of rare earth elements (REE) and their fractionation patterns, major elements, Pb Hg were determined in two multicores collected at 445 2100 m water depth (mwd) the Cascais submarine canyon (CSC). The PAAS-normalized REE patterns suggest mixing Tagus estuarine marine sediments, marked by MREE (Nd?Dy series) enrichment positive Eu-anomaly, with sediments. Eu/Eu* implies incor...
Characterization of caprock shale is critical in CO2 storage site evaluation because the acts as a barrier for injected buoyant plume. The properties shales are complex and influenced by various processes; hence, it challenging to evaluate quality. An integrated approach therefore necessary assessing seal integrity. In this study, we investigated Lower Jurassic Drake Formation from proposed Aur...
—Foraminiferal tests are a common component of many marine sediments. The oxygen isotope ratio (δ18O) of test calcite is frequently used to reconstruct aspects of their life environment. The δ18O depends mainly on the isotope ratio of the water it is precipitated from, the temperature of calcification, and, to a lesser extent, the carbonate ion concentration. Foraminifera and other organisms ca...
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