O are claimed to be pieces of ocean crust and upper mantle that have been thrust up onto continental crust and are now found in mountains, mainly along continental margins.1,2 An ideal ophiolite suite consists from bottom to top of peridotite, gabbro, sheeted dikes, basalt with pillow lavas and sedimentary rocks. The peridotite is considered to be an upper mantle rock, while the remainder of th...

ONE petrological approach to upper mant le studies is to determine which ultramafic rocks represent mantle material. Ultramafic rocks occur in a variety of field and petrographic associations : in recent reviews, Wyllie [1967b, 1968] outlined eleven petrographic associations, some with subdivisions. In this summary, it is convenient to consider these in four larger groups: (1) layered, stratifo...

In situ laser ablation inductively coupled mass spectrometry (LA ICP-MS) is used to determine the U-Th-Pb age of phosphates ferromerrillite and apatite in Los Angeles shergottitic meteorite. The initial 207Pb/206Pb was refined by analyzing K-rich diaplectic glass. LA ICP-MS mapping document zones elevated U Th content establish textural controls on isotope ages. By critically assessing dispersi...

First posted July 19, 2023 For additional information, contact: Center Director, Geophysics, and Geochemistry Science CenterU.S. Geological SurveyBox 25046, Mail Stop 973Denver, CO 80225 Compressional-wave seismic velocity (velocity) bulk density (density) data were compiled from published sources for rock suites earth materials that are significant geophysical modeling of the Mesoproterozoic M...