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The role of boron and fluids in high temperature, shallow level metamorphism of the Chugach Metamorphic Complex, Alaska

Author:
Leeman, W. P.
Published:
JAN 1, 1988.
Physical Description:
1 electronic document
Additional Creators:
Sisson, V. B.
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Summary:
The possible role of boron (B) involvement in granite equilibria and generation of melts during crustal metamorphism has been a focus of speculation in recent literature. Most of the evidence for such involvement derives from experimental data which implies that the addition of B will lower the temperature of the granite solidus. Also the presence of tourmaline has a minor effect on the temperature of the solidus. Further indirect evidence that B may be involved in partial melting processes is the observation that granulites are commonly depleted in B, whereas the B content of low grade metapelites can be high (up to 2000 ppm). Researchers' measurements of the whole-rock B contents of granulites from the Madras region, India are low, ranging from 0.4 to 2.6 ppm. Ahmad and Wilson suggest that B was mobilized in the fluid phase during granulite facies metamorphism of the Broken Hill Complex, Australia. Thus, it appears that during the amphibolite to granulite transition, B is systematically lost from metasediments. The B that is released will probably partition into the vapor phase and/or melt phase. Preliminary measurements imply that the boron content of rocks in the Chugach Metamorphic Complex is not sufficient to influence the processes of partial melting at low pressures.
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Collection:
NASA Technical Reports Server (NTRS) Collection.
Note:
Document ID: 19890012879.
Accession ID: 89N22250.
Lunar and Planetary Inst., Workshop on the Deep Continental Crust of South India; p 165-167.
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