40Ar/39Ar dating of plutonic/metamorphic rocks from Chinmen Island off southeast China and its tectonic implications
Publication Year
1993
Type
Journal Article
Abstract
To reconstruct the thermal history of the Yanshanian Orogeny in SE China, a combination of 40Ar/39Ar thermochronological and thermobarometrical techniques have been performed on hornblende, biotite and K-feldspar separates from a granite and gneiss sample from Chinmen Island. Based on closure temperature calculations and the isotopic dates of the minerals, the thermal history of the area is derived as follows: the region experienced plutonism/metamorphism prior to 101 Ma, cooled rapidly in the initial stages at a rate of 80°C/Ma between 101 and 97 Ma, and then cooled slowly to 180°C at a rate of 8°C/Ma until 82 Ma. The fast cooling may reflect rapid tectonic uplifting. However, the plutonic/metamorphic complex was not exposed at the surface until the Miocene. A paleo-geothermal gradient of about 30°C/km has also been inferred. -from Authors
Keywords
Journal
Journal - Geological Society of China
Volume
36
Pages
35-55