Discovery and geological significance of hyaloclastite of Batamayineishan Formation in Eastern Junggar Basin

Key words:  eastern Junggar Basin  Batamayineishan Formation  Hyaloclastite  source rock  subaquatic eruption  zircon U-Pb age

Abstract:

Hyaloclastite is a type of volcanic rock that results from magma erupting under water or quenching abruptly with water contact. Hyaloclastite of Batamayineishan Formation that develops in Baijiangou is studied using field profile measurements, thin section authentication, LA-ICP-MS zircon U-Pb dating and source rock analysis. The results show that the hyaloclastite can be divided into two categories, including rhyolitic hyaloclastite and basaltic hyaloclastite. This provides a direct evidence for the subaquatic eruption environment of volcanic rocks in Wucaiwan and Baijiangou. The rhyolitic hyaloclastite formed at 333.8±4.6 Ma ago in the Early Carboniferous. Combining the results of previous studies, the volcanic rocks of Batamayineishan Formation were developed in both Early Carboniferous and Late Carboniferous.The under-water eruption probably began in the Early Carboniferous(333.8±4.6 Ma) and continued to the Late Carboniferous(300.4±1.3 Ma).Long duration of under water eruptions increased the organic abundance of source rock, and the organic acid which was released by thermal evolution of organic matter further resulted in secondary dissolution pores in the reservoir.