--> --> Abstract: The Depositional History of the Mangas Conglomerate, Grant County, Southwestern New Mexico, by J. D. Griffin; #90925 (1999)

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GRIFFIN, JOY D., The University of Texas at Austin, Dept. of Geological Sciences, Austin, TX

Abstract: The Depositional History of the Mangas Conglomerate, Grant County, Southwestern New Mexico

The Mangas Graben, located southwest of Silver City in southwestern New Mexico, is situated at the triple junction of the Rio Grande rift, the Colorado Plateau, and the Basin and Range. Volcanism and erosion of surrounding highlands filled the Mangas Graben during the late Neogene, depositing as much as 800 m of Mangas conglomerate. The goal of this project is to identify the source of the Mangas sediments, document its depositional architecture, and determine the timing of deposition of the conglomerate. This will provide insight into paleoclimate, drainage patterns, and local tectonics, such as rate, direction, and magnitude of extension.

The Mangas conglomerate has been extensively mapped in the area; however, little is known about its deposition. The study of this conglomerate will encompass an area of 11 km2 in the immediate vicinity of the Tyrone copper mine. A model of the depositional history will be developed using lithology of the clasts, grain size variation, sedimentary structures, nature of the contacts, and lateral extent of the beds. Volcanics interbedded with the conglomerate will be dated using 40Ar/39Ar and undergo provenance studies for possible correlation with similar rocks in the region.

In addition to the large-scale copper mining by Phelps Dodge of the Tyrone ore body, the Mangas is currently being mined for exotic deposits consisting of copper oxides. In addition to its economic importance in mineral exploration, a depositional study of the conglomerate is significant for developing models of rift sedimentation, particularly for hydrocarbon exploration. 

AAPG Search and Discovery Article #90925©1999 AAPG Foundation Grants-in-Aid