Mw. Zhao et al., THERMAL AND TECTONIC HISTORY OF THE ORDOS BASIN, CHINA - EVIDENCE FROM APATITE FISSION-TRACK ANALYSIS, VITRINITE REFLECTANCE, AND K-AR DATING, AAPG bulletin, 80(7), 1996, pp. 1110-1134
Citations number
84
Categorie Soggetti
Energy & Fuels","Geosciences, Interdisciplinary","Engineering, Petroleum
Apatite fission track analysis, vitrinite reflectance data, and K-Ar d
ating of Permian-Carboniferous and Mesozoic core samples have been suc
cessfully integrated to reconstruct the thermal and tectonic history o
f the Ordos basin, China, Apatite fission track ages of Carboniferous-
Jurassic sedimentary rocks range between 3 and 137 Ma, and are signifi
cantly younger than the stratigraphic ages. Confined fission track len
gths demonstrate exclusively mixed length distribution, indicating com
plex thermal history. The data suggest that the samples-must have all
experienced higher paleotemperatures in the past, Mean vitrinite refle
ctance values (R(o)) of the Triassic rocks range from 0.61 to 1.06%, g
iving a high coalification gradient of 0.36%/km and suggesting a high
paleothermal gradient of 57 degrees C/km. Permian-Carboniferous rocks
have R(o) values on the order of 1.0-3.0%, and locally up to 4.0-6.0%,
Some high R(o) values coincide with positive gravity and magnetic ano
malies, K-Ar dating on Permian-Triassic samples reveals distinct illit
ization at 170-160 Ma, during which a thermal event occurred due to su
bsurface magmatic intrusion related to the early Yanshanian movement,
The petroleum source rocks of the Upper Triassic experienced peak temp
eratures ranging from 90 to 160 degrees C, corresponding to the oil wi
ndow, and Permian-Carboniferous source rocks were heated to more than
150 degrees C, passing through and out of the gas window. Due to rapid
uplift and erosion in response to the rise of the Qinghai-Tibet plate
au associated with the Asia-India collision and the Himalayan orogeny,
cooling has taken place at least since approximately 23 Ma, The diffe
rence in the rate and amount of uplift between the eastern and western
parts of the basin resulted in differential uplift and the present-da
y structural pattern of the basin.