Abstract:

Apatite fissiontrack analysis offers the opportunity to reveal Mesocenozoic tectonothermal history of different sections and different sequences in the Northeast of Ordos Basin，and to provide new constraints on forecast and prospect oil, gas and other mineral. Simulation results show that: the temperature of stratum slowly rose at the rate of 09 ℃/Ma during 250-150 Ma; and rapidly rose at the rate of 21 ℃/Ma during 150-120 Ma in the northeast of Ordos Basin. At this time, all temperatures that are higher than 130 ℃ reach the highest. After that, strata of the north margin in the northeast of Ordos Basin rapidly uplift and cool at the rate of 13 ℃/Ma during 120-65 Ma and slowly uplift and cool at the rate of 04 ℃/Ma during 65-10 Ma; and strata of the south margin and subsidence of basin slowly uplift and cool at the rate of 09 ℃/Ma during 120-30 Ma and rapidly uplift and cool at the rate of 15 ℃/Ma during 30-10 Ma. The northeast of basin rapidly uplift and cool at the rate of 65 ℃/Ma since at least 10 Ma. Therefore, it is considered that （120±10) Ma is the key time of MidYanshan tectonic thermal event, which brought about the mature hydrocarbon generation and the largescale petroleum accumulation in the northeast of Ordos Basin. The north margin passed the 110 ℃ closed temperature in the 65 Ma±, and the south margin and subsidence area passed 110℃ closed temperature in the 30 Ma±, which were beneficial to the protopetroleum enrichment and preservation. Since Paleogene late (30 Ma), especially Neogene late (10 Ma), the rapid upliftcooling process has most probably become the key factor of the protopetroleum adjustment and the secondary reservoir formation.

Key words: Northeast of Ordos Basin, Mesocenozoic, apatite fission track, tectonothermal history