Eclogite-facies fluid infiltration: constraints from δ18O zoning in garnet

Autor: Ashley K. Russell, John W. Valley, Kouki Kitajima, Ariel Strickland, L. Gordon Medaris, Daniel J. Schulze
Rok vydání: 2012
Předmět:
Zdroj: Contributions to Mineralogy and Petrology. 165:103-116
ISSN: 1432-0967
0010-7999
DOI: 10.1007/s00410-012-0794-9
Popis: In situ analysis reveals that eclogite-facies garnets are zoned in δ18O with lower values in the core and rims that are ~1.5 to 2.5 ‰ higher. This pattern is present in 9 out of 12 garnets analyzed by SIMS from four orogenic eclogite terranes, and correlates with an increase in the mole fraction of pyrope and Mg/Fe ratio from core to rim, indicating prograde garnet growth. At the maximum temperatures and the time-scales experienced by these garnets, calculated intragranular diffusion distances for oxygen are small ( 5 ‰) from two kimberlites are homogeneous in δ18O, possibly due to diffusive exchange, which is possible for prolonged periods at higher mantle temperatures. Homogeneity of δ18O in garnets outside the normal mantle range (5–6 ‰) may be common in kimberlitic samples.
Databáze: OpenAIRE
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