115-7 Trace Element Bulk Geochemistry of Magnetite-Bearing Intermediate Volcanic Units, Knight Range, Grant County, New Mexico

Session: Petrology, Volcanology, and Mantle Plumes across the Solar System (Posters)

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Abstract:

The intermediate to felsic volcanic units exposed in the Knight Range of southwestern New Mexico formed during the Tertiary ignimbrite flare-up, yet most remain uncorrelated with the region’s major volcanic fields. The Knight Range is a northeast-dipping block of Cretaceous-Tertiary volcanic, volcaniclastic, and sedimentary units that outcrop within the Gila National Forest in Grant County. It is situated within the Basin and Range province, between the Mogollon-Datil volcanic field to the north and the Boot Heel volcanic field to the south.

This study investigates three andesitic units: the JPB Mountain andesite, the Malpais Hills andesite, and an andesitic dike, here termed the Juniper dike, that cross-cuts underlying units. Although no contacts or connections are observed between the Juniper dike and the overlying andesites, it may represent a feeder dike to either unit. Of additional interest, all three andesitic units contain magnetite that is disseminated and/or defines a foliation-like texture, which is posited to be the result of post-crystallization hydrothermal alteration. The goals of this study are to 1) clarify the relationships among these units, 2) study evidence of possible secondary mineralization, and 3) build a dataset that may be used for regional correlation.

While recent work identified similarities in mineralogy and major element geochemistry between the Juniper dike and both andesitic units, the data were inconclusive. Trace element bulk compositions were collected alongside major element data via handheld X-ray fluorescence spectrometry (hXRF) of powdered samples. These trace element data will be analyzed to identify similarities and compositional trends within and between these units. Preliminary results support a correlation between the Juniper dike and the overlying JPB Mountain andesite.

Geological Society of America Abstracts with Program. Vol. 57, No. 6, 2025

doi: 10.1130/abs/2025AM-11237

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