Titanite: U-Pb Dating and Applications on Defining P-T-t Path of Metamorphic Rocks

摘要: The stability of titanite is controlled by pressure,temperature,compositions the bulk rock and coexisting fluid,activity H2O,fugacity O2.Titanite a common accessory mineral in large range rocks.It widespread magmatic rocks with high Ca/Al ratio.It appears different metamorphic ranging from greenschist facies,blueschist facies amphibolite facies.Its may extend into eclogite-facies high-pressure granulite-facies calcic rocks.Because its U structure closure temperature(upper limit amphibolite-faces),titanite an ideal U-Pb dating mineral.In contrast to zircon,titanite(composed mainly Ca Ti) quite reactive most contain Ti at conditions.Therefore,its ages are likely yield age crystallization rather than resetting simple diffusion,such that preserve complicated system contains information whole history rock,which can be revealed situ dating,e.g.,SHRIMP,LA-MC-ICP-MS LA-ICP-MS.Importantly,Zr concentration sensitive temperature pressure,and accordingly Zr good thermobarometer.Both assemblages equilibrium titanite-Zr thermobarometer used determine pressure temperature.Consequently,P-T-t paths metamorphism defined combination ages.