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Petrological and geochemical investigations at the Cajon Pass Deep Drillhole
Author(s) -
Silver Leon T.,
James Eric W.,
Chappell Bruce W.
Publication year - 1988
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/gl015i009p00961
Subject(s) - geology , lithology , cretaceous , geochemistry , pluton , crust , mantle (geology) , tectonics , basement , petrology , mineralogy , seismology , paleontology , civil engineering , engineering
Chemical analyses of cores from the Cajon Pass Deep Drillhole confirm vertical lithologic diversity of the basement rocks. They are metaluminous and calcalkaline; weak major element correlations with wide‐ranging SiO 2 suggest they are not a simple cogenetic suite. Quartz contents correlate with the thermal gradient profile, supporting conduction as the principal thermal transport mechanism. Abundances of heat producing elements are variable and somewhat lower than average crustal values. Cross‐calibration with other measures of Th, U and K are underway. Ages of surface granitoids and core 17 are late Cretaceous; other plutonic rocks appear older but late Mesozoic. Initial lead isotopic signatures of the plutonic rocks change dramatically with depth in the hole.