Premium
Redistribution of U and TH in shallow plutonic environments
Author(s) -
Gosnold William D.
Publication year - 1987
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/gl014i003p00291
Subject(s) - pluton , batholith , geology , geochemistry , groundwater , hydrothermal circulation , meteoric water , radiogenic nuclide , tectonics , mantle (geology) , paleontology , geotechnical engineering
Radioactive heat production in the Idaho Batholith and in the Alamosa River Stock in the San Juan Mountains correlates with the degree of hydrothermal alteration of plutons by meteoric groundwater. Fission‐track mapping shows that as much as half of the U in whole‐rock samples of the most‐intensively‐altered zone of the Alamosa River Stock is associated with secondary minerals. The hydrothermally‐altered, shallow plutons in the Idaho Batholith contain significant amounts of U in secondary minerals whereas unaltered, deeply‐emplaced plutons contain virtually all of their U in primary accessory minerals. The relative distributions of U and Th measured by gamma‐ray spectrometry, the associations of U observed by fission‐track mapping and a depth‐dependence in thermally‐induced hydraulic fracturing suggest a depth‐dependent geochemical process that could produce an upward increase in the abundance of U and Th in batholiths. The process adds U and Th to chemically‐receptive secondary minerals during alteration of plutons by convecting groundwater.