The Study Of Cryptoexplosive Breccia Pipe Features And Zircon Chronology Of Heishiwan,Moate,Xinjiang

Moate, Xinjiang is located in the eastern segment of Xiemisitai in the northern margin of the western Junggar, and has good prospects of the copper polymetallic ore. In this paper, the research works mainly around the occurrence characteristics of Heishiwan cryptoexplosive breccia pipe, petrologic and geochemical characteristics, and the rock-forming age. We also carry out the intial exploration of diagenetic mechanism of breccia. The main understanding are as follows:1. Cryptoexplosive breccia was firstly discovered in Moate orefield. Through field and laboratory observations, this cryptoexplosive breccia pipe was multiple including basaltic and rhyolite cryptoexplosive breccia pipe.2. In order to determine the formation age of the cryptoexplosive breccia, we dated the Heishiwan cryptoexplosive breccia and got the age of 382-387Ma, which formed in the early to middle Devonian in the late Paleozoic. Inherited zircon (605Ma in the core part) suggests that there may exist Precambrian ancient crust.3. Geochemical characteristics of the basaltic cryptoexplosive breccia suggest that the source of alkaline basalts may have experienced metasomatism of carbonate melt or fluid. Anomaly or unobvious positive anomaly of Eu suggest that the fractional crystallization of feldspar did not occur in the basaltic magma. The REE characteristics of zircons from the rhyolitic cryptoexplosive breccia were magmatic origin, also some hydrothermal zircons.4. The trace features of zircons from rhyolitic cryptoexplosive breccia suggest that it was formed in a continental environment, tectonic setting of volcanic arc and the intraplate volcanics, indicating the rhyolitic magma were formed on the transition zone where the oceanic crust subducted to continental crust, which has a mixture source of oceanic crust and continental crust.5. According to the theory of Metallogenic Theory through Trans-magmatic Fluids (MTTF), fluid can dramatically alter the physical properties of the melt, in particular density and viscosity. The density makes the magma get greater buoyancy. The activity of fluid resulted in strong activation of magma chamber, thereby basaltic magma blasted earlier than rhyolitic magma. Rhyolitic cryptoexplosive breccia imply that at least one basaltic and one granitic magma chamber exist in the area. The magma-fluid events in the Heishiwan area are as follows:intrusion of granite porphyry ? shear deformation of granite porphyry ? alteration by iron-rich fluid ? basaltic magma cryptoexplosion ? rhyolitic magma cryptoexplosion ? fluid activity of silicon-rich.