A major element geochemical study of Laramide igneous rocks of the Colorado mineral belt
Lux, Daniel R.
Burchfiel, B. C.
Master of Arts
Major element chemical analyses for igneous rock samples from the Colorado mineral belt are presented along with chemical analyses from the literature. Petrographic data which was collected is also presented. Samples range from basaltic to granitic compositions but rocks with intermediate silica contents are most common. Data indicates that these rocks have calcalkaline characteristics, with the exception of one sample which is silica-undersaturated. Lead and strontium isotopic data taken from the literature, suggest that source materials in the lower crust are 17 to 18 m.y. old. The association in time and space suggest Laramide structural deformation and igenous activity are related. However, it appears that Precambrian structures control the emplacement of Laramide igneous rocks along the Colorado mineral belt. Distribution of ore deposits and Pb isotopic values for ores are in agreement with partial melting of Precambrian lower crust. Models involving the generation of Laramide igneous rocks by melting along a subduction zone are considered unfavorable.