Journal of Asian Earth Sciences

Dolomitization;Mg isotope;Pore genesis;Dominant control factors;Penglaiba Formation;Tarim Basin

The source and driving mechanism of Mg-rich fluids in the dolomitization process of the Lower OrdovicianPenglaiba Formation in the Tarim Basin have not been effectively traced, limiting the accuracy of the predictionof high-quality dolomite reservoirs, In this study, based on Mg isotopes combined with petrology, trace elementsand C-0-Sr isotopes, the powder crystalline dolomite (D1) and fine crystalline dolomite (D2) of the PenglaibaFormation were found to have high Na and Sr contents and low Fe and Mn contents. The REE, $l3c, $180 and87Sr/s6sr ratios ranges were similar to those of seawater, and $'Mg shows a steady downward trend. Thedolomitization fluids of D1 and D2 were derived from seawater and migrated vertically downward. Penecontemporaneous dolomitization is beneficial for the inheritance and preservation of original rock pores. The Naand Sr contents of medium crystalline dolomite (D3) and coarse rystalline dolomite (D4) were low, whereas theFe and vin contents were high. The REE, $+80 and s7sr $6sr ratios difered from those of seawater, and s26Mgshows a fluctuating trend, The fluids for the precipitation of D3 and D4 were sourced from concentrated marinepore water during burial, with the dolomitization fluid migrating through intergranular pores and structuraliractures. Burial dolomitization has preservation, adjustment, and transformation effects on dolomite reservoirs.Deep high-quality dolomite reservoirs are not only controlled by the original sedimentary environment, but isalso affected by late-stage or subsequent burial transformation.

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SCI