Emplacement age of the post- orogenic A-type granites in Northwestern Lesser Xing/an Ranges, and its relationship to The eastward extension of Suo- Lushan-Hegenshan-Zhalaite Collisional suture zone

摘要

A great amount of alkali-feldspar and alkaline granites have been found around Nenjiang, Northwest Lesser Xing/an Ranges, but their forming ages have been a Controversial subject due to the lack of reliable geological And isotopic geochronological evidence. The zircon U-Pb Isotopic dating results conducted in this note indicate that These granites emplaced at 260 - 290 Ma, coeval with the late Stage of Late Paleozoic. Studies of mineralogy, petrology and Geochemistry show that they are post-orogenic A-type gran- Ites, and consist of the northeastern extension of huge belt of Southeast Mongolia-Central Inner Mongolia. Therefore, we Can determine that the Suolunshan-Hegenshan-Zhalaite Collisional suture zone extends northeastward to Heihe with The collision age of Carboniferous.