The great depth and relatively steep geothermal gradient (3⁄429oC=km) of the KTB deep crustal borehole, located in the Bavarian region of Germany, provides the basis for our study of diffusive argon loss in K-feldspar. The observed borehole temperature at 9 km is 3⁄4265oC which reaches well into the argon closure interval for K-feldspar (3⁄4125–350oC). Four microcline and two adularia samples d...

B. Turrin et al. (1) argue that conventional K-Ar and 4Ar/39Ar age determinations and paleomagnetic data provide a definitive age assignment of approximately 136 ka (thousand years ago) to 141 ka for the Lathrop Wells volcanic center with an error of less than 10,000 years. This conclusion is tendered despite replicate age determinations that extend over almost three orders of magnitude. Turrin...

This study compiles the U-Pb and 40Ar/39Ar geochronology of metasedimentary, migmatitic granitic rocks Sierra Albarrana Domain, based on data recently published by authors together with other bibliographic sources. Maximum depositional ages (MDA) magmatic metamorphic events are discussed. MDAs suggest that this domain was deposited during middle Cambrian (ca. 511) zoned zircon grains indicate m...