Abstract:

MongoliaHinggan Orogen is an important metallogenic belt of China; many Modeposits were discovered in this belt recently owing to the great deal of input by government and companies. But the regional geological background of Modeposits remains unknown. Based on the study of igneous rocks, the regional geological maps and Modeposits, this paper reaches the following conclusions: (1) The Indosinian orogeny and Yanshanian orogeny are independent orogenic cycles; the Indosinian orogeny was ended at about 220200 Ma, which is marked by a suit of alkaline, peralkaline and miarolitic granites in the area; furthermore, the Yanshanian orogeny was started from the earlyJurraic and went into postorogeny at the late of earlyCretaceous, which is marked by another suit of alkaline, peralkaline and miarolitic granites in the area, as Baerzhe pluton, Alongshan pluton, etc..  (2) There are mainly two Mo metallogenic epochs in Yanshanian era: about 180 Ma and about 130 Ma; 180 Ma is the early time of Yanshanian orogeny, the deposits of this time were mainly CuMo deposits and the correlated igneous petrotectonic assemblage is  Tonalitegranodioritegranitegranodiorite porphyrygranite porphyry etc.; 130 Ma is the late time of Yanshanian orogeny, the deposits were mainly Mo（W/U）deposits and the correlated igneous petrotectonic assemblage is finegrained granitegranite porphyryquartz porphyryfelstone etc.. (3) About four regional compressionthrust events can be recognized: after J1, after J2, after J3 and after K1; the unconformity sediments of K2 had covered all of above thrust tectonics and the compressionthrust events were over. So, the formation of Modeposits of the Yanshanian was under the background of compressionthrust, rather than the background of continental rift by extension of lithosphere.

Key words: MongoliaHinggan Orogen, series of magmatictectonicMo metallogenic events, Mesozoic Era, metallogenic epoch, compressionthrust events