Rb-Sr and U-Pb isotopic studies of the two contrasting granite types of the Dauzhai and Luobuli massifs in South China provide new constraints on the interpretation of isotopic age data for plutonic igneous rocks.A Rb...Rb-Sr and U-Pb isotopic studies of the two contrasting granite types of the Dauzhai and Luobuli massifs in South China provide new constraints on the interpretation of isotopic age data for plutonic igneous rocks.A Rb-Sr internal isochron age of 146±7Ma for the Luobuli adamelligte is interpreted to represent the age of magma crystallization,whereas the whold-rock Rb-Sr isochron yields an older apparent age of 161±10Ma which is regarded as resulting from contamination processes affecting the petrogenesis of 161±10Ma which is regarded as resulting from contamination processes affecting the petrogenesis of this adamellite.In the Daguzhai granite the marked scatter of whole-rock Rb-Sr data in isochron diagram is ascribed to the open sstem behavior of Rb during postmagmatic autometasomatism.Uniformity of intital ^87Sr/^86Sr ratio in this granite is indicated in a plot of ^87 Sr versus ^86Sr.The autometasomatism has also affected zircon U-Pb system ,resulting in a spread of data along the Concordia.curve between 165 and 125Ma.This spread is regarded as indicating the duration the autometasomatism.展开更多
文摘Rb-Sr and U-Pb isotopic studies of the two contrasting granite types of the Dauzhai and Luobuli massifs in South China provide new constraints on the interpretation of isotopic age data for plutonic igneous rocks.A Rb-Sr internal isochron age of 146±7Ma for the Luobuli adamelligte is interpreted to represent the age of magma crystallization,whereas the whold-rock Rb-Sr isochron yields an older apparent age of 161±10Ma which is regarded as resulting from contamination processes affecting the petrogenesis of 161±10Ma which is regarded as resulting from contamination processes affecting the petrogenesis of this adamellite.In the Daguzhai granite the marked scatter of whole-rock Rb-Sr data in isochron diagram is ascribed to the open sstem behavior of Rb during postmagmatic autometasomatism.Uniformity of intital ^87Sr/^86Sr ratio in this granite is indicated in a plot of ^87 Sr versus ^86Sr.The autometasomatism has also affected zircon U-Pb system ,resulting in a spread of data along the Concordia.curve between 165 and 125Ma.This spread is regarded as indicating the duration the autometasomatism.
