Temporal relations of volcanism and hydrothermal systems in two areas of the Jemez volcanic field, New Mexico

Journal Article · Wed Nov 01 04:00:00 EST 1989 · Geology; (USA)

DOI:https://doi.org/10.1130/0091-7613(1989)017<0986:TROVAH>2.3.CO;2· OSTI ID:6159403

WoldeGabriel, G; Goff, F ^[1]

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1. Los Alamos National Laboratory, NM (USA)

Two hydrothermal alteration events (8.07 Ma, one sample; 6.51-5.60 Ma, six samples) related to the waning stages of late Miocene volcanism ({ge} 13 to {le} 5.8 Ma) are recognized at the Cochiti district (southeast Jemez Mountains). Most of the K/Ar dates (0.83 {plus minus} 0.11-0.66 {plus minus} 0.21 Ma, four samples) in the hydrothermally altered, caldera-fill rocks of core hole VC-2A at Sulfur Springs, Valles caldera, indicate post-Valles caldera hydrothermal alteration. A sample from acid-altered landslide debris of postcaldera tuffs from the upper 13 m of the core hole was too young to be dated by the K/Ar method and is possibly associated with current hot-spring activity and the youngest pulses of volcanism. Oxygen-isotope data from illite/smectite clays in the Cochiti district are zonally distributed and range from {minus}2.15{per thousand} to {plus}7.97{per thousand} (SMOW), depending upon temperature, extent of rock-fluid interaction, and composition. The samples from VC-2A get lighter with depth ({minus}0.20{per thousand} to {plus}1.62{per thousand}). The K/Ar and oxygen-isotope data provide strong evidence that the epithermal quartz-vein-hosted gold-silver mineralization at Cochiti and the sub-ore grade molybdenite at VC-2A were deposited in the late Miocene (5.99-5.60 Ma) and mid-Quaternary ({approximately}0.66 Ma), respectively, by hydrothermal fluids composed primarily of meteoric water.

• OSTI ID: 6159403
• Journal Information: Geology; (USA), Journal Name: Geology; (USA) Vol. 17:11; ISSN GLGYB; ISSN 0091-7613
• Country of Publication: United States
• Language: English

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