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Experimental Studies of Igneous Rock Series: Felsic Body Suite from the Needle Point Pluton, Wallowa Batholith, Oregon

Piwinskii, A. J. and Wyllie, P. J. (1970) Experimental Studies of Igneous Rock Series: Felsic Body Suite from the Needle Point Pluton, Wallowa Batholith, Oregon. Journal of Geology, 78 (1). pp. 52-76. ISSN 0022-1376.

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The phase relationships of four analyzed granitic rocks which comprise a late-stage felsic body sequence intruding the Mesozoic granodiorites and tonalites of the Needle Point pluton, Wallowa Batholith, Oregon, have been determined in the presence of 15 wt percent water at pressures to 3 kbar. Pressure-temperature curves were located for the beginning of melting, and for the disappearance of K-feldspar, quartz, plagio-clase, biotite, and hornblende in granodiorite no. 678, quartz monzonites nos. 685 and 774, and granite no. 705. Compositions and structural states of plagioclases from the granitic rocks, basic masses intruding the batholith, and mafic inclusions, as well as the compositions of coexisting feldspars, were determined using the electron microprobe analyzer. Variations in each of these parameters throughout the melting interval of each granitic rock were measured at 2 kbar pressure. Although experimental conditions (excess H_2O present; fO_2 regulated but not controlled) forbid detailed comparison with natural occurrences, the results indicate that, at 2 kbar pressure, temperatures of at least 730° C and 780° C are required to generate liquids of granite and quartz monzonite composition. Several factors suggest that the normal product of partial fusion of many crustal rock types is a H_2O-undersaturated granite liquid; crystal mushes with this type of liquid are probably involved if intermediate magmas are derived from crustal sources.

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Additional Information:© 1970 University of Chicago Press. Manuscript received March 27, 1969; revised June 17, 1969. We thank W. H. Taubeneck for his generosity in providing the rock samples, together with a host of chemical and modal data that made the samples suitable for experimental examination. C. Wayne Burnham, J. Shade, and R.F.C. Martin kindly performed a few runs in internally heated pressure vessels. The research was supported by the National Science Foundation with grant GA-923. Financial support for Piwinskii was provided by a Fannie and John Hertz Foundation fellowship and NSF postdoctoral fellowship. This support is gratefully acknowledged.
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Fannie and John Hertz FoundationUNSPECIFIED
NSF Postdoctoral FellowshipUNSPECIFIED
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Official Citation:Piwinskii, A. J., and P. J. Wyllie. “Experimental Studies of Igneous Rock Series: Felsic Body Suite from the Needle Point Pluton, Wallowa Batholith, Oregon”. The Journal of Geology 78.1 (1970): 52–76
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:64165
Deposited By: Tony Diaz
Deposited On:03 Feb 2016 23:32
Last Modified:03 Oct 2019 09:35

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