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Fluid‐mediated modification of garnet interiors under ultrahigh‐pressure conditions
Author(s) -
Perchuk Alexei L.,
Burchard Michael,
Maresch Walter V.,
Schertl HansPeter
Publication year - 2005
Publication title -
terra nova
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.353
H-Index - 89
eISSN - 1365-3121
pISSN - 0954-4879
DOI - 10.1111/j.1365-3121.2005.00647.x
Subject(s) - massif , geology , metamorphic rock , fluid inclusions , eclogite , geochemistry , recrystallization (geology) , quartz , terrane , mineralogy , mineral , petrology , subduction , materials science , seismology , tectonics , metallurgy , paleontology
We report the results of a novel experimental study on eclogitic garnets with abundant inclusions of clinozoisite, quartz and rutile subjected to temperatures ( T ) of 800–1100 °C and a pressure ( P ) of 4 GPa, representative of ultrahigh‐pressure (UHP) metamorphic terranes such as the Kokchetav massif, Saxonian Erzgebirge, etc. The experiments reveal extremely rapid recrystallization and partial melting of garnet interiors controlled by fluids liberated from the breakdown of the hydrous mineral inclusions. The traditional assumption that inclusions of minerals and primary fluid inclusions should be representative of the peak or even earlier metamorphic history cannot be strictly applied in this case. We argue that inclusions in UHP garnets may mirror P – T conditions postdating growth of the host crystal or even P – T conditions never actually experienced by the rock itself. The above modification of garnet interiors produces a typical patchy microstructure that occurs in natural eclogitic garnet from the diamond‐bearing UHP Kokchetav massif.