| Geology and Mineral Resources of the East Mojave National Scenic Area, San Bernardino County, California Contributor(s): U. S. Department of the Interior (Author) |
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ISBN: 1499234775 ISBN-13: 9781499234770 Publisher: Createspace Independent Publishing Platform OUR PRICE: $18.04 Product Type: Paperback Published: April 2014 |
| Additional Information |
| BISAC Categories: - Reference |
| Physical Information: 0.58" H x 8.5" W x 11.02" (1.41 lbs) 274 pages |
| Descriptions, Reviews, Etc. |
| Publisher Description: The rocks of the East Mojave National Scenic Area (EMNSA) record a history of dynamic geologic events that span more than 1,800 million years (m.y.). These geologic events contributed significantly to development of the spectacular vistas and panoramas present in the area today. The oldest rocks underlie much of the northern part of the EMNSA. These rocks were subjected to extreme pressures and temperatures deep in the Earth's crust about 1,700 million years ago (Ma). They were subsequently intruded by granitic magmas from about 1,695 to 1,650 Ma, by additional granitic magmas at about 1,400 Ma and, later, at about 1,100 Ma, by iron-rich magmas that crystallized to form dark igneous rocks termed diabase. Unusual potassium- and magnesium-rich rocks, emplaced at about 1,400 Ma, crop out in a few places within and near the EMNSA. Their distinctive composition results from very small degrees of partial melting of mantle peridotite that was highly enriched in incompatible trace elements. At Mountain Pass, just outside the northeast boundary of the EMNSA, the potassium- and magnesium-rich rocks are accompanied by a rare type of carbonatite, an igneous rock composed of carbonate minerals, that contains high-grade rare earth element mineralization. |
