Characteristics and origin of the Ediacaran peperites in the northwestern Tarim Basin, and their geological implications

Key words: 
• Tarim Basin /
• Ediacaran Series /
• Peperite /
• Volcanic eruption /
• Littoral subaqueous sedimentary environment.

Abstract: Peperite is a kind of transitional rock formed by the syngenetic mixing of hot magmatic materials and wet and cold unconsolidated sediments, which has important paleoenvironmental implications. Based on outcrop geological survey and microscopic petrological analysis, typical peperites are recognized in Ediacaran basic volcanic rocks in northwestern Tarim Basin, which mainly include blocky peperites and fluidal peperites, and their host is purplish red sandy sediments. The peperites were mainly formed by the intrusion of magma into the water-rich unconsolidated sandy sediments or by the flow of magma on the surface of the water-rich unconsolidated sandy sediments. Among them, the thinner magmatic intrusion and the bottom of the surface flood basalt mainly formed the fluidal peperites, while the thicker magmatic intrusion developed the blocky peperites. It is concluded that the northern margin of the Tarim craton was still in an intraplate rift setting related to the breakup of the Rodinia supercontinent during the early Ediacaran, and the development of peperite indicates that the basalt eruption in this area was mainly in a littoral subaqueous sedimentary environment; with the end of volcanic eruption, the northern Tarim Craton transformed into a relatively stable passive continental margin basin or a cratonic basin during the late Ediacaran.