ICE IN LATE DARRIWILIAN?

Halite fluid inclusions from the Mizhi drilling holes in the North Shaanxi Basin are studied with respect to characteristics, hydrogen and oxygen isotopic compositions and package play flow components, so as to restore the ancient sedimentary environment, and to discuss the material supply on this basis. The δ¹⁸O and δ D values of water in the primary halite inclusions in simple liquid phase reflect the isotopic compositions during each salt crystallization stage in the ancient brine water lake, which can be considered basis for prediction of the brine evolution. The δ¹⁸O and δ D is so negative , the lowest of the δ D is about -158‰ most of the data is about -120 ,it is very lower ,theδ¹⁸O has the same negative trend , the minimum -13.2‰ to the maximum -0.2‰Hydrogen and oxygen isotopic compositions of the halite inclusions show the deposition was supplied by multiple provenances, including thermal fluids. The study on the fluid compositions in the Ordovician halite inclusions indicates that the ancient sea water could allow the deposition of the potassium magnesium salt rocks at that time, the macro element of K⁺ has a content of 5.93 g/L - 23.24 g/L, averaging about 15.24 g/L, and for Ca²⁺ and Mg²⁺,averaging 1.40 g/L and 17.70 g/L, respectively; and for the trace elements Li, B, Rb, Sr, 63.77 mg/L, 1.51 mg/L, 5.45 mg/L, 83.88 g/L.

In this study, that the deposition of the MajiagouV member in the North Shaanxi Basin was supplied by transgressive sea water, as well as by thermal fluids. On the other hand, the frequent transgression during the Majiagou deposition affected the preservation of the potassium magnesium salt. The δ¹⁸O and δ D show some ice water have been there .So, In late Darriwilian ,some ice have been in the north China block.