Mafic inclusions in Yosemite granites and Lassen Pk lavas: records of complex crust-mantle interactions
This study compares three small-scale magmatic systems dominated by mafic/felsic interaction that appear to be analogs to the evolution of their larger host systems: mafic inclusions from modern Lassen Pk lavas along with inclusions and related synplutonic dike materials from granitoids in the Tuolumne Intrusive Series. Each system represents quickly chilled mafic melt previously contaminated by digestion of rewarmed, super-solidus felsic hosts. Contaminants occur in part as megacrysts of reworked oligoclase with lesser hb and biot. Within each group MgO-variation diagrams for Fe, Ca, Ti, Si are strikingly linear (r>.96); alkalis are decidedly less regular, and many hybrid rocks show a curious, pronounced Na enrichment. Field data, petrography, and best fit modeling suggests this may result from flow concentration of oligoclase xenocrysts within contaminated synplutonic dikes, and is preserved in the inclusions when dike cores chill as pillows in their felsic host. Dissolution of mafic inclusions erases these anomalies and creates a more regular series of two-component mafic-felsic mixtures in the large host system. The inclusions and dikes thus appear to record a variety of late-stage mafic-felsic interactive processes that earlier and on a larger scale created much of the compositional variety of their intermediate host rocks.
- Research Organization:
- Hampshire College, Amherst, MA (USA)
- OSTI ID:
- 6460681
- Report Number(s):
- CONF-8510489-
- Journal Information:
- Geol. Soc. Am., Abstr. Programs; (United States), Vol. 17; Conference: 98. annual meeting of the Geological Society of America, Orlando, FL, USA, 28 Oct 1985
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
CALIFORNIA
VOLCANIC ROCKS
CHEMICAL COMPOSITION
PETROGENESIS
PETROLOGY
EARTH MANTLE
FELDSPARS
GEOCHEMISTRY
GEOLOGIC HISTORY
GEOLOGIC MODELS
GRANITES
MAGMATISM
MINERALOGY
PETROGRAPHY
VOLCANISM
CHEMISTRY
FEDERAL REGION IX
GEOLOGY
IGNEOUS ROCKS
MINERALS
NORTH AMERICA
PLUTONIC ROCKS
ROCKS
USA
580300* - Mineralogy
Petrology
& Rock Mechanics- (-1989)
580400 - Geochemistry- (-1989)