The petrological characteristics and tectonic implications of turbidite and seismite in Balagedai tectonic melange belt, Inner Mongolia: Take regional geological survey scaled 1:50000 in Halahei area, Inner Mongolia as an example

The turbidite is the ancient trench sediments with Bouma series. And part of the sediment is closely related to the ancient trench earthquake. Due to oceanic plate subduction and volcanic eruption, the seismic activities are intense and frequent at the trench. The Sedimentary rocks are constantly disturbed by earthquakes during diagenetic process at this area. So, the seismites recording seismic activities are formed. By studying the turbidite and seismite in Balagedai tectonic melange belt, we recognize the turbidite sequence and the seismite sequence. The turbidite sequence includes flushing molds such as ditch mold and flute cast with graded bedding, convolute bedding, and the black silty mudstone at the top sequence. The seismite sequence includes fluidized vein, shattered breccia, slump breccia, seismic crimp, laminar or stepped fault, etc. Then we establish the identification marks of turbidite and seismite rocks. Furthermore, we restored the paleotectonic environment of Dashizhai Formation at study area. And the former Dashizhai Formation divided by predecessor should be broken up. Dashizhai Formation is the turbidite sediment at the ancient trench in the arcfront basin. Considering the volcanics, basic rocks or ultrabasic rocks in Huashi Hill in the turbidite, we get the conclusion that, due to plate collision, the turbidite, arc volcanic rocks and oceanic sediments are bunched together by a series of thrust faults. So the tectonic melange is formed. This provide evidence that Erlian-Heihe suture zone extends eastern to the study area.