E.H. McKee S.J. Martel B. D. Turrin P. Segall 1990 <div id="15572972" class="article-section-wrapper js-article-section js-content-section " data-section-parent-id="0"><p>Regional sets of steeply dipping joints and faults are common throughout the Sierra Nevada batholith, yet relatively little is known about how or when they formed. Within some east-northeast-striking, left-lateral fault zones in the Mount Abbot quadrangle of the central Sierra Nevada, the host granodiorite is hydrothermally altered to a lower greenschist assemblage that contains muscovite. The muscovite yields a mean K-Ar and<span>&nbsp;</span>⁴⁰Ar/³⁹Ar age of 79 Ma, which provides a minimum age for the faulting. Field relations show that these faults developed from earlier formed, mineralized joints, so these ages also provide a minimum age for the jointing. Published ages of biotite, hornblende, and zircon from the host granodiorite of Lake Edison are 80 Ma (K-Ar), 85 Ma (K-Ar), and 90 Ma (U-Pb), respectively. The geochronology, field relations, and hydrothermal mineral assemblages together suggest that the mineralized joints and faults all formed between 85 and 79 Ma, soon after the host pluton was emplaced.</p></div> application/pdf 10.1130/0091-7613(1990)018<1248:LCAOFI>2.3.CO;2 en Geological Society of America Late Cretaceous age of fractures in the Sierra Nevada batholith, California article