Tracing of detrital provenance of Late Triassic Strata in the "Golden Triangle" area of Yunnan, Guizhou and Guangxi

Triassic strata are most widely distributed rock series in Yunnan, Guizhou and Guangxi, and host various low-temperature mineral resources such as Carlin type gold deposits.Previous studies of the Triassic stratigraphic provenance in this area are quite rich; nevertheless, they are mainly concentrated on the Early and Middle Triassic strata, but lack the data on clastic provenance of late Triassic strata.Therefore, on the basis of previous studies, the U-Pb age of detrital zircons in the study area was measured by LA-ICP-MS analysis technology.The results show that most zircons have magmatic zones with Th/U ratios higher than 0.4.The U-Pb ages of zircons are concentrated in 308~396 Ma, 440~680 Ma, 727~930 Ma, 1004~1266 Ma, 1400~1880 Ma and 2360~2724 Ma.By comparing the age distribution characteristics of detrital zircons between the study area and the surrounding blocks and in combination with the lithofacies palaeogeography, palaeo-ocean current and palaeo-current, the authors hold that the provenance of the study area was mainly from the North Vietnam Palaeocontinent.At the same time, the tectonic mountain system of Hunan, Guangdong, Guangxi and Yunkai area probably also provided some provenances.The provenance proves that the Paleo-Tethyan Ocean was closed gradually during the Indosinian period, and the South China block collided with the Indosinian block along the Songma suture zone.