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GEOREF RECORD

Geochemistry of the Bonito Lake Stock, Lincoln County, New Mexico; petrogenesis and hydrothermal alteration

James Constantopoulos
Geochemistry of the Bonito Lake Stock, Lincoln County, New Mexico; petrogenesis and hydrothermal alteration
Rocky Mountain Geology (December 2007) 42 (2): 137-155

Abstract

The Bonito Lake stock is one of three stocks that intrude the Sierra Blanca Volcanics in the Nogal-Bonito mining district of New Mexico. The 26.6-Ma stock consists primarily of porphyritic syenite with subordinate quartz syenite and monzonite. SiO (sub 2) concentrations range from 54 to 66 weight percent. Na (sub 2) O exceeds K (sub 2) O and combined alkalis average 9.4 weight percent. The rocks are alkaline and metaluminous and plot in the syenite and syenodiorite fields on an R (sub 1) R (sub 2) multicationic plot. The chondrite-normalized extended trace element diagram has a negative slope with Ba values 167 to 286 times chondritic values and Yb values eight to 14 times chondritic values. The chondrite-normalized REE plot has a negative slope with mild LREE enrichment. (La/Yb) (sub N) values range from 15 to 22 and the mean Eu/Eu (super *) is 0.91. Clinopyroxene, zircon, and apatite fractionation, along with feldspar accumulation were the most important factors in controlling elemental abundances. Quasi Pearce Element Ratio (PER) analysis confirms the role of clinopyroxene fractionation, as well as indicates that an increase in K and a loss of Ca+ or -Na occurred during alteration. The quasi PER analysis also shows that the rocks are slightly metasomatized. Whole-rock delta (super 18) O values for the Bonito Lake stock range from 2.0 to 8.4 per mil. Oxygen isotope values for the more permeable surrounding volcanic rocks range from 1.0 to 7.8 per mil. The lower values of the volcanic rocks are reflective of meteoric-hydrothermal water interaction. These data help us better understand not only this stock, but also the Sierra Blanca igneous complex and the Lincoln County Porphyry Belt. This study also contributes to our understanding of the Nogal-Bonito mining district and the larger Rocky Mountain alkalic province.


ISSN: 1555-7332
EISSN: 1555-7340
Serial Title: Rocky Mountain Geology
Serial Volume: 42
Serial Issue: 2
Title: Geochemistry of the Bonito Lake Stock, Lincoln County, New Mexico; petrogenesis and hydrothermal alteration
Affiliation: Eastern New Mexico University, Department of Physical Sciences, Portales, NM, United States
Pages: 137-155
Published: 200712
Text Language: English
Publisher: University of Wyoming, Dept. of Geology and Geophysics, Laramie, WY, United States
References: 39
Accession Number: 2008-045196
Categories: Isotope geochemistryIgneous and metamorphic petrology
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. 4 tables, sketch map
N33°07'60" - N34°21'00", W106°22'00" - W104°54'00"
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute. Abstract, copyright, University of Wyoming. Reference includes data from GeoScienceWorld, Alexandria, VA, United States
Update Code: 200813
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