Heavy mineral distribution regularity of Paleogene detrital rocks in Lanping basin, Yunnan Province

The analytical results of 59 Paleogene sandstone samples from Lanping basin indicate that the average content of stable heavy minerals is 38.4%, the relatively stable and unstable minerals are very rare, respectively possessing 2.3% and 1.1%. The average content of the facies minerals hematite and limonite is high, possessing about 50.5%. According to stability coefficient, ZTR index, ATi index and the variation characteristics of heavy mineral index along the profile, the tectonic evolution is divided into two periods: flat period and active period. The tectonic activities of different parts and periods of the basin show some differences; on the whole, the activity of south central basin was later than that of the north basin in time. The heavy mineral assemblage suggests that the Paleogene provenance had several kinds of rock styles, dominated by sedimentary rock, with minor basic rock, intermediate-acidic intrusive rock and metamorphic rock. From east to west, the ZTR index decreases gradually. In combination with tectonic setting of the study area and previous research findings on the basement of the basin, the authors infer that, in Yunlong period, the provenance mainly came from the eastern margin of the basin, and the provenance of Guolang Group mainly came from the eastern margin of the basin, followed by the western margin. The facies of heavy mineral assemblage shows that the ancient sedimentary environment of Lanpin basin was a strong oxidation environment of swallow water.