Silurian seismites in Hanxia, Yumen, North Qilian Mountains, and their tectonic significance

The Caledonian orogenic belt of the North Qilian Mountains is an intensely active structure belt. In the process of the Late Caledonian syn-orogeny, t he North Qilian-Hexi Corridor area was situated on the tectonic background of a syn-orogenic basin. In response to the orogenic process of the North Q ilian Mountains, typical earthquake event deposits-seismites of the Siluria n were widely distributed around Hanxia of Yumen City, the Liyuan River of Sunan County and Biandukou of Minle County. In the Hanxia area, where seism ites are typically developed, elastic deposits of tidal-flat facies are the background deposits of the Hanxia Formation. The earthquake event deposits are characterized by sandy mudstone veins, synsedimentary microfractures, micro-corrugated laminations and earthquake breccias, which in turn constit ute complex seismites, featuring seismic corrugation, shattering and liquef ied sandy mudstone veins, auto-clastic breccias and intraclastic parabrecci as. The seismites and tidal flat deposits formed typical sequences of earth quake event deposits.