Formation of layered and schlieren migmatites by partial melting at Aspen Basin, New Mexico
Conference
·
· Geol. Soc. Am., Abstr. Programs; (United States)
OSTI ID:6317977
Although several recent studies of layered migmatites have suggested that they originated by subsolidus differentiation, both layered and schlieren-type migmatites at Aspen Basin formed by partial melting. Proterozoic supracrustal rocks at Aspen Basin were intruded by a suite of calc-alkalic diorite, tonalite and granite, intensely deformed, then intruded by younger aplite and granite. The supra-crustal rocks consist of migmatitic, sillimanite-grade metagreywacke, felsic gneiss and amphibolite. Within the metagreywackes, concordant coarse-grained neosomes (leucosomes + melanosomes) are interlayered with fine-grained grey gneiss. These layered migmatites grade toward schlieren-type migamtites at deeper levels, where the proportions of leucocratic material and degree of discordance increase. Two pieces of evidence demonstrate that leucosomes crystallized from melts. Partial melting is favored over injection on the basis of major and trace element chemical analyses. None of the plutonic units have appropriate composition to serve as the migmatite source, and the chemical and mineralogical compositions of leucosomes and leucogranites correlate to their metamorphic host rock, implying local derivation. The transition from layered to schlieren migmatites is marked by an increase in Rb, Rb/Sr, and K/sub 2/O/Na/sub 2/O within the leucosomes and leucogranites, and apparently represents an increase in the degree of partial melting.
- Research Organization:
- Univ. of New Mexico, Albuquerque (USA)
- OSTI ID:
- 6317977
- Report Number(s):
- CONF-8510489-
- Conference Information:
- Journal Name: Geol. Soc. Am., Abstr. Programs; (United States) Journal Volume: 17
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
58 GEOSCIENCES
580300* -- Mineralogy
Petrology
& Rock Mechanics-- (-1989)
580400 -- Geochemistry-- (-1989)
ALKALI METALS
ALKALINE EARTH METALS
CHEMICAL COMPOSITION
CHEMISTRY
ELEMENTS
FEDERAL REGION VI
GEOCHEMISTRY
GEOLOGIC AGES
GEOLOGIC STRUCTURES
GEOLOGY
GNEISSES
IGNEOUS ROCKS
MAGMATISM
MELTING
METALS
METAMORPHIC ROCKS
METAMORPHISM
MINERALOGY
NEW MEXICO
NORTH AMERICA
PETROGENESIS
PETROLOGY
PHASE TRANSFORMATIONS
PRECAMBRIAN ERA
ROCKS
RUBIDIUM
SEDIMENTARY BASINS
STRONTIUM
USA
580300* -- Mineralogy
Petrology
& Rock Mechanics-- (-1989)
580400 -- Geochemistry-- (-1989)
ALKALI METALS
ALKALINE EARTH METALS
CHEMICAL COMPOSITION
CHEMISTRY
ELEMENTS
FEDERAL REGION VI
GEOCHEMISTRY
GEOLOGIC AGES
GEOLOGIC STRUCTURES
GEOLOGY
GNEISSES
IGNEOUS ROCKS
MAGMATISM
MELTING
METALS
METAMORPHIC ROCKS
METAMORPHISM
MINERALOGY
NEW MEXICO
NORTH AMERICA
PETROGENESIS
PETROLOGY
PHASE TRANSFORMATIONS
PRECAMBRIAN ERA
ROCKS
RUBIDIUM
SEDIMENTARY BASINS
STRONTIUM
USA