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Direct observation of adakite melts generated in the lower continental crust, Fiordland, New Zealand
Author(s) -
Stevenson James A.,
Daczko Nathan R.,
Clarke Geoffrey L.,
Pearson Norman,
Klepeis Keith A.
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.1365-3121.2004.00586.x
Subject(s) - adakite , geology , mafic , continental crust , geochemistry , partial melting , oceanic crust , crust , subduction , underplating , mantle wedge , petrology , granulite , geomorphology , paleontology , tectonics , facies , structural basin
Adakites have a distinct chemistry that links them to melting of a mafic source at high pressure. They have been attributed to melting of subducted oceanic crust or melting of the mafic crustal roots of thick continental arcs, and are an important contrast to mantle wedge melting as a means of generating continental crust. We report the first direct evidence for the generation of adakitic melts in mafic lower continental crust, in an exhumed Cretaceous arc in the South Island of New Zealand. The lower crustal Pembroke Granulite has the bulk chemistry and partial melting textures involving peritectic garnet appropriate for a source region for an adakitic melt. The melt migrated from the area through a fracture network now filled with trondhjemitic veins. Emplacement of the melt was in the upper crust of the Cretaceous section, illustrated by the presence of coeval adakites in the upper crustal Nelson‐Westland region.