Abstract:

Based on the LA-ICP-MS zircon dating of the basement granite from the well Bincan 1, the characters of the basement in the Sanjiang basin are discussed. Zircons from the granite of the well Bincan 1 are euhedral to subhedral in shape and show the typical oscillatory zoning, which indicates their magmatic origin. Their Th/U ratios ranging from 0.22 to 0.82 imply that they derived from crystallization of magma.²⁰⁶Pb/²³⁸U ages of zircons from the granite are between 427 Ma and 502 Ma, weighted mean ²⁰⁶Pb/²³⁸U ages are subdivided into two groups, i.e., (430±8) Ma and (496±6) Ma, respectively. The age of (430±8) Ma represents the formation time of the basement granite beneath the Suibin depression, i.e., the Early Silurian, whereas the age of (496±6) Ma represents the timing of captured zircons during the formation of granitic magma and/or magmatic emplacement. These captured zircons are  temporally consistent with the Mashan Group and the PanAfrican gneissic granites within the Jiamusi massif. It’s concluded that the there occur Calidonian granites within the basin basement. Moreover, the basement beneath the Suibin depression within the Sanjiang basin has the same geological features as the Jiamusi massif.

Key words: Sanjiang basin, Suibin depression, basement, granite, LA-ICP-MS, zircon U-Pb dating, Jiamusi massif