The clay mineralogical composition and illite cyrstallinity were measured,with the samples from the Lizhou-Hekou section in Tianlin county and the Mingshan gold ore deposit in Lingyun county, and with D/max-2500 apparatus and the XRD measuring standard of SY/T 5163 1995. According to the Kübler index of illite crystallinity, the Early Triassic Luolou Group to the Middle Triassic low member of Baifeng Formation belonged to epizone with K.IΔ2θ° being 0.22; the Middle Triassic upper member of the Baifeng Formation and the Hekou Formation belonged to anchizone, among them the former as high anchizone with K.IΔ2θ° being 0.26～0.33, and the Hekou Formation as low anchizone with K.IΔ2θ° being 0.38～0.40. Additionally, it was possible that there was a diagenitic zone in the upper strata. It could be deduced that very low-grade regional burying metamorphism happened in the Lizhou-Hekou region, because the metamorphic grade was concordant with the location of the rocks, and the metamorphic grade boundary line was nearly same as the strata boundary line in the strata column. The Kübler index of illite crystallinity in the Mingshan gold ore deposit were 0.42～0.52 which belonged to diagenitic zone, and with no concordant with strata, which showed the characters of the gold metallogenitic hydrothermal alteration illite during the Yanshanian cycle after the regional burial metamorphism.
Yan Shouxun,Wang Zhigang,Huang Yongquan. VERY LOW-GRADE REGIONAL METAMORPHISM IN THE YOUJIANG REGION, WESTERN GUANGXI, USING ILLITE CRYSTALLINITY[J]. Chinese Journal of Geology, 2003, (1): 107-113,106.