Abstract:

Because of the large time span and the age overlap of the lithostratigraphic units of Mesozoic volcanic rocks in southern
Great Hingan Range, we have chosen volcanic rocks from Hongshanzi Basin to measure the SHRIMP zircon U-Pb age, together
with the zircon U-Pb age of the volcanic rocks from adjacent area and the characteristics of rock associations to correlate the
volcanic rock series . The zircon in two alkaline rhyolite samples (sample numbers HS505, HS102) and one high-k calc-alkaline
rhyolite samples (sample numbers HS601) from Hongshanzi Basin has obvious oscillatory ring, high Th/U ratio, and they belong
to typical magma genesis. The results of zircon U-Pb dating indicate that the ²⁰⁶Pb/²³⁸U age range of 10 analysis points of sample
HS601 is 150~160 Ma with the weighted average of 156.5±1.6 Ma and MSWD of 1.11. Eleven analysis points of sample
HS102 is 153~159 Ma with the weighted average of 154.7±1.7 Ma and MSWD of 0.77. Fourteen analysis points of samples
HS505 is 151~160 Ma with the weighted average of 156.5±1.4 Ma and MSWD of 1.16. The age range of the volcanic rocks
from Hongshanzi Basin is 157~155 Ma, which belongs to the early Late Jurassic. The volcanic rocks in Hongshanzi Basin show characteristics of high-k calc-alkaline rhyolite-alkaline rhyolite associations, which are similar to those of the Xinmin Formation.
The volcanic rocks are also stratigraphically correlatable. Therefore, the volcanic rocks should belong to the Xinmin Formation.
The Late Jurassic felsic volcanic rocks in southern Great Hingan Range, which was previously assigned to Manketouerbo
Formation and Manitu Formation, should belong to the Xinmin Formation, and the age of the revised Xinmin Formation is similar
to that of mafic volcanic rocks of Tiaojishan Formation or Lanqi Formation in northern Hebei-western Liaoning and Tamulan
Formation in northern Great Hingan Range, showing two zones, northerly and southerly, of rock association of the Late Jurassic
volcanic rock in Northeast China.

Key words: Xinmin Formation, SHRIMP zircon U-Pb age, early Late Jurassic, lithostratigraphical correlation, southern Great Hingan Range