40Ar/39Ar plateau age spectra of feldspars and their geological implications
The paragenic minerals plagioclase. perthite, biotite, hornblende and pyroxene in acid-granite, alkali-granite, monzonite and volcanic rocks collected from seven areas different in thermal history have been determined. On the basis of 14 plateau age spectra and isochron ages of paragenic minerals in conjunction with the observed mineral textures, the suitability of plateau age spectra of plagioclase and perthite and their thermo-chronological significance are discussed in this paper.
The results indicate that undisturbed feldspar gives satisfactory40Ar-39Ar plateau ages in consistence with those of paragenic minerals. This means that feldspars from the undisturbed area are suitable for40Ar-39Ar dating. On the other hand. the age spectra of feldspars as well as of biotite. pyroxene and hornblende affected by tectonic or thermodynamic events appear unsmooth at varying temperatures, thus complicating their interpretation. Feldspars may give an emplacement age of a rock and /or that of the latest thermodynamic event, depending on the intensity of the event and the retentivity of Ar in the mineral.
KeywordsJunggar Basin Paragenic Mineral Release Percent Intermediate Temperature Range Damiao Anorthosite
Unable to display preview. Download preview PDF.
- Dai Tongmo et al., 1986, The collision and thermo-tectonic history of Indian-Sunda-Eurasian plates inferred from40Ar-39Ar age spectra of granodiorite: Geochimica, n. 2, p. 97–102 (in Chinese).Google Scholar
- Hong Dawei et al., 1987, Petrogenesis of the miarolitic granites in the coastal area of Fujian: Beijing, Science and Technological Press (in Chinese).Google Scholar
- Hu Shiling et al., 1990, Isotopic ages and REE geochemistry of Damiao anorthosite: Geoscience, n. 2, p. 332–342 (in Chinese).Google Scholar