Paleosalinity analysis and trace element geochemistry of Chang 6 member in Gengwan-Shijiawan area, Ordos Basin
Online published: 2007-12-15
The trace element geochemistry methods such as B, Sr, Rb and K+Na mass fraction, Sr/ Ba ratio, Rb/K ratio combining with clay mineral X -ray diffraction analysis are applied to analyze the paleosalinity of Chang 6 in Gengwan-Shijiawan area. The result shows that in the period of Chang 6 stage, it is fresh -mildly brackish environment, partly brackish environment with the paleosalinity from 0.014‰ to 6.47‰ , average of 2.56‰, and the water is saltier gradually from the period of Chang 63 to Chang 61. The paleosalinity isolines are mapped after recovering the paleosalinity quantitatively, in which three paleosalinity zones are divided, including fresh water zone, mildly brackish water zone and brackish water zone. And 0.5‰ isoline is determined to be the position of lake shoreline which is the boundary of fresh water river and mildly brackish lake. The mildly brackish water and close environment are favorable for the development of the high quality source rocks, and could promote the forming of the early chlorite rim cementation to retard the compaction and dissolution which is helpful for preserving primary intergranular pores. So it provides important evidence for the favorable target prediction of lithostratigraphic reservoirs.
ZHANG Liqiu . Paleosalinity analysis and trace element geochemistry of Chang 6 member in Gengwan-Shijiawan area, Ordos Basin[J]. Lithologic Reservoirs, 2007 , 19(4) : 20 -26 . DOI: 10.3969/j.issn.1673-8926.2007.04.004
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