| Pingluo Construction Zone in western Sichuan depression formed in the Triassic tectonic movements,is China's important K-rich brine storage areas. Lei Koupo group is one of the layers of K-rich brine mass produced in the area.This paper through to analysis strontium isotopes of Lei Koupo group in the study area FengLu1 well, Explored Leikoupo carbonate formation during the halogen source contribution and the evolution of sedimentary environment in the area, As well as the formation of K-rich brine may be imposed by the impact of the late Deep hydrothermal activity and so on,and provided some basis for research the cause of the late K-rich brine in Sichuan.(1)The variation range of (87)~Sr/(86)~Sr of Triassic Lei Koupo Formation marine carbonate in Pingluo Construction Zone in western Sichuan depression is 0.704769-0.708376, This is due to tectonic uplift of the leading Indo Sichuan Basin from the "ocean basin"to"bowl alone" evolution, resulting in sea water and ocean basin separated by a closed sea sedimentary environment, and gradually shallow water basin, and the mine mouth Slope of the late end of the marine deposits, sedimentary environment, the transition from the shallow continental opposite, that the material deposition in the number of sources of water contribute to the material in sea water from the source to accept more terrigenous material to receive more, resulting in the Triassic basin Discipline is different from the global marine sedimentary carbonate strontium isotopic composition of the update with the times showed an increasing tendency.(2)(87)~Sr/(86)~Sr of marine carbonate on Leikoupo Formation of Triassic in Pingluo Construction Zone is low and span a larger range of values. Besides large-scale end-Permian eruption of the Emeishan basalts led to lower (87)~Sr/(86)~Sr values , the main The reason is that the brine activities have a greater degree of relationship in late with the different sections: with the strong-related areas of brine , (87)~Sr/(86)~Sr grows lower; by minimal impact of brine activities, the strontium isotope composition of seawater with the European Alps range of Sr isotope ratio (0.707 75-0.708 30) is broadly similar on the same period.(3)(87)~Sr/(86)~Sr of Leikoupo Formation in Pingluo Construction Zone rises slowly in the overall trend ,and highlights two consecutive low and high cycles. (87)~Sr/(86)~Sr in different cycles correspond to different lithology. In Leikoupo the second and third and Leikoupo four paragraphs of the last sub-section, depth 5338.5-4933.5 m and depth of 4720-4480 m values were relatively low (87)~Sr/(86)~Sr two cycles, the ratio at 0.705 546-0.706 975 and 0.70503-0.70619, corresponding to both the dolomite rock gypsum rock folder. While the other two cycles of high (87)~Sr/(86)~Sr values appear in the next sub-section of mine four paragraphs 4913.5-4740 m and 4460-4420 m Lei five sections, the ratio of 0.706 and 0.707 212-0.708 168-0.708 01, corresponding to lithology folder for the gypsum rock dolomite and limestone dolomite.Well water level drop text from geochemistry and Fenglu NO. 1 well brine, Pingluo NO. 4 well which runs through the Longmen Shan fault zone a few deep latent faults in the north west can be seen rising later hydrothermal activity along the fault zone into the deep material, to a certain extent changed the original source of the relative proportions of carbonate Sr, resulting in the (87)~Sr/(86)~Sr values change. Clip cream dolomite rock Leikoupo the second and third and Leikoupo sub-section of the upper four paragraphs of strontium isotope ratio is mainly due to exceptionally low, dolomite and gypsum compared to more developed pore , water permeability is relatively strong, the transformation by the late hydrothermal activity has become even more intense. The gypsum rock structure is relatively more dense dolomite, most of the performance of the resisting strong degree of influence by later hydrothermal smaller Leikoupo four paragraphs in the section under the sub-folder cream dolomite rock strata in the strontium isotope ratios to folder than dolomite formation in the gypsum rock influence to be small.And in the area the difference of porosity of dolomite is larg (0.45% -11.77%), therefore, the dolomite layers with different pore size, the development of fissures in varying degrees, by the late hydrothermal alteration of the degree of influence is not As a result all the dolomite rock gypsum rock folder Leikoupo three sections and Leikoupo four paragraphs on the sub-section of the low level of strontium isotope ratios are not the same. It is a direct result of these two reasons Leikoupo strontium isotope ratio in the overall upward trend, the formation of two low-high cycle regularly change.It can be seen, K-rich high-pressure hot brine formation in the western basin Closely related to the structural belt along the Bay of hydrothermal activity, the hot brine storage and activities of strontium isotopic composition of carbonate changes, to some extent reflect the Deep hydrothermal formation of its important influence exerted. The enormous energy from deep hydrothermal upwelling, gradually increase the brine temperature of carbonate reservoirs , and help the original polyhalite and the other potassium minerals decomposing to further enrich potassium ions in the brine. |
PDF Full Text Request