Geologic temperature

Collect all available data (geographical, hydrological, geological, temperatures, chemical and isotopic compositions, time variations, and so on). 

LA-ICP-MS using a multi-collector instrument for Pb-Pb dating via ° Pb/ °" Pb and ° Pb/ ° Pb isotope ratio measurements of natural rutile crystals has been utilized to study geological temperature-time histories. The significance of Devonian-Carboniferous igneous activity in Tasmania on the basis of U-Pb dating has been measured by sensitive high resolution ion microprobe (SHRIMP). ... 

Fig. 1. General distribution of GOR as a function of reservoir temperature, North Sea. Shaded areas represent GORs of fluids at reservoir temperatures below 150 C. Black lines describe GOR evolution predicted by MSSV pyrolysis of source rock samples at geological temperatures, dashed line instantaneous phase, bold line cumulative phase. The circles show fluid GORs of HPHT reservoirs.

Several conditions need to be satisfied for the existence of a hydrocarbon accumulation, as indicated in Figure 2.1. The first of these is an area in which a suitable sequence of rocks has accumulated over geologic time, the sedimentary basin. Within that sequence there needs to be a high content of organic matter, the source rock. Through elevated temperatures and pressures these rocks must have reached maturation, the condition at which hydrocarbons are expelled from the source rock. 

Dissolution and replacement. Some minerals, in particular carbonates, are not chemically stable over a range of pressures, temperatures and pH. Therefore there will be a tendency over geologic time to change to a more stable variety as shown in Figure 5.12. 

Alkanes from CH to C4gFlg2 typically appear in crude oil, and represent up to 20% of the oil by volume. The alkanes are largely chemically inert (hence the name paraffins, meaning little affinity), owing to the fact that the carbon bonds are fully saturated and therefore cannot be broken to form new bonds with other atoms. This probably explains why they remain unchanged over long periods of geological time, despite their exposure to elevated temperatures and pressures. 

Decomposition of Zircon. Zircon is a highly refractory mineral as shown by its geological stabiUty the ore is cracked only with strong reagents and high temperature. 

Seam correlations, measurements of rank and geologic history, interpretation of petroleum (qv) formation with coal deposits, prediction of coke properties, and detection of coal oxidation can be deterrnined from petrographic analysis. Constituents of seams can be observed over considerable distances, permitting the correlation of seam profiles in coal basins. Measurements of vitrinite reflectance within a seam permit mapping of variations in thermal and tectonic histories. Figure 2 indicates the relationship of vitrinite reflectance to maximum temperatures and effective heating time in the seam (11,15). 

A method of estimating original gas in place using the results of drilling (structural assessment, effective thickness, porosity, gas saturation, pressure, temperature, gas characteristics, and the boundaries of the accumulation). These data may be supplemented by geological or geophysical data on the shape of the reservoir. 

Sorption of plutonium (l.fixlO-11 M) and americium (2xl0-9 M) in artificial groundwater (salt concentration 300 mg/liter total carbonate 120 mg/liter Ref. 59) on some geologic minerals, quartz, biotite, o apatite, o attapulgite, montmorillonite. Dashed lines indicate the range for major minerals in igneous rocks. Experimental conditions room temperature, particle size 0.04-0.06 mm, solid/liquid ratio 6-10 g/1, aerated system, contact time 6 days. 

I emphasized and seconded what Rai called out - namely the great need for experimental work to determine solubility data for plutonium in its various oxidation states under typical expected geologic repository conditions (e.g., pH, Eh, temperature, etc.). 

Fig. 18-8 Characteristic temperature-depth distributions at an ice divide. For a climatic temperature history as shown in (a) the temperature-depth distribution changes as shown in (b). Following the step increase in surface temperature, the initial steady temperature profile (fi in (b)) is altered by a warming wave (e.g., at time fa) but eventually reaches a new steady profile by time t. (c) Temperature data from Greenland measured by Gary Clow of the US Geological Survey, showing wiggles due to climate variations (Cuffey et ah, 1995).

Epstein, S., Buchsbaum, R, Lowenstam, H. and Urey, H.C. 1951 Carbonate-water isotopic temperature scale. Bulletin of the Geological Society of America 62 417-425. 

Grossman, E. and Ku, T.-L. 1986 Oxygen and carbon isotope fractionation in biogenic aragonite temperature effects. Chemical Geology (Isotope Geoscience Section) 59 59-74. 

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