Mobility of elements during K-metasomatism of volcanic rocks by alkaline, saline brines

Conference · Wed Jan 01 04:00:00 EST 1992 · Geological Society of America, Abstracts with Programs; (United States)

OSTI ID:5931770

Chapin, C E ^[1]

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1. New Mexico Bureau of Mines and Mineral Resources, Socorro, NM (United States)

Silicic ignimbrites and interbedded mafic lavas of Oligocene age were altered by alkaline, saline brines in the Popotosa basin of the Rio Grande rift near Socorro, New Mexico. Alteration was toward a fine-grained assemblage of adularia + hematite [+-] quartz irrespective of initial rock composition. Elevated [delta][sup 18]O and the occurrence of zeolites, gypsum, and salt casts in overlying play a deposits indicates that the altering fluids were basin brines. Preliminary analysis of secondary inclusions in fractured quartz phenocrysts indicates temperatures near 100 C and salinities near 20 wt. % NaCl equivalent. To test element mobility, pairs of fresh and altered samples from each of 7 ignimbrite units plus 4 samples of interbedded mafic lavas were analyzed by XRF, INAA, and AA. The elements showing the greatest mobility during alteration of ignimbrites are listed below along with their enrichment factors (altered rock/fresh rock). Ignimbrites: enriched--K[sub 2]O 1.99, Rb 1.89, Ba 1.43, As 12.14, Sb 18.30, Pb 1.23; depleted--Na[sub 2]O 0.25, MgO 0.57, CaO 0.27, MnO 0.50, P[sub 2]O[sub 5] 0.75, Sr 0.54, Li 0.57, U 0.78, Br 0.67, Cu 0.90, Zn 0.69. The dramatic enrichment of As and Sb in both ignimbrites and mafic lavas indicates that these elements are highly mobile in oxidizing basin brine systems. K-metasomatism is a common type of alteration in rift basins, detachment terranes, aquifers through which brines have migrated.

• OSTI ID: 5931770
• Report Number(s): CONF-921058--
• Conference Information: Journal Name: Geological Society of America, Abstracts with Programs; (United States) Journal Volume: 24:7
• Country of Publication: United States
• Language: English

Related Subjects

58 GEOSCIENCES
580000* -- Geosciences
ALKALI METAL COMPOUNDS
ALKALI METALS
ALKALINE EARTH METALS
ANTIMONY
ARSENIC
BARIUM
BRINES
CHALCOGENIDES
DEVELOPED COUNTRIES
ELEMENTS
ENRICHMENT
ENVIRONMENTAL TRANSPORT
GEOLOGIC STRUCTURES
LAVA
LEAD
MASS TRANSFER
METALS
METAMORPHISM
MINERALOGY
NEW MEXICO
NORTH AMERICA
OXIDES
OXYGEN COMPOUNDS
POTASSIUM COMPOUNDS
POTASSIUM OXIDES
RESERVOIR TEMPERATURE
RIFT ZONES
RUBIDIUM
SALINITY
SEMIMETALS
USA
VOLCANIC REGIONS