Reference Database (ERR)
Development and Maintenance by the Database Team

Detailed Reference Information
Streck & Grunder 1997
Streck, M.J. and Grunder, A.L. (1997). Compositional gradients and gaps in high-silica rhyolites of the Rattlesnake Tuff, Oregon. Journal of Petrology 38(1): 133-163.
The Rattlesnake Tuff of eastern Oregon comprises >99% of high-silica rhyolite glass shards and pumices representing similar to 280 km(3) of magma. Glassy, crystal-poor, high-silica rhyolite pumices and glass shards cluster in five chemical groups that range in color from white to dark gray with increasing Fe concentration. Compositional clusters are defined by Fe, Ti, LREE, Ba, Eu, Rb, Zr, Hf, Ta, and Th. Progressive changes with increasing degree of evolution of the magma occur in modal mineralogy, mineral composition, and partition coefficients. Partition coefficients are reported for alkali feldspar, clinopyroxene, and titanomagnetite. Models of modal crystal fractionation, assimilation, successive partial melting, and mixing of end members cannot account for the chemical variations among rhyolite compositions. On the other hand, similar to 50% fractionation of observed phenocryst compositions in non-modal proportions agrees with chemical variations among rhyolite compositions. Such non-modal fractionation might occur along the roof and margins of a magma chamber and would yield compositions of removed solids ranging from syenitic to granitic. A differentiation sequence is proposed by which each more evolved composition is derived from the previous, less evolved liquid by fractionation and accumulation, occurring mainly along the roof of a slab-like magma chamber. As a layer of derivative magma reaches a critical thickness, a new layer is formed, generating a compositionally and density stratified magma chamber.

Kd's Database



Table 1A
Table 1B
Table 1C
Table 1D
Table 1E
Table 1F
Table 1G
Table 2
Table 3A
Table 3B
Table 4A
Table 4B
Table 5
Table 6
Table 7

Analysis & Mineral Preparation

high-silica rhyolite, partition coefficients, rhyolite differentiation, zoned ash-flow tuff, layered convection, element partition-coefficients, zoned magma chambers, rare-earth elements, trace-element, new-mexico, fractional crystallization, caldera, liquid, evolution, dynamics
Journal of Petrology
Oxford University Press
Great Clarendon Street
Oxford OX2 6DP
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