Middle Proterozoic mafic magmatism, east central Idaho: Implications for age of deposition of Belt Supergroup and basin subsidence models

Conference · Thu Apr 01 00:00:00 EST 1993 · Geological Society of America, Abstracts with Programs; (United States)

OSTI ID:5421776

Chamberlain, K R ^[1]; Doughty, P T ^[2]

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1. Univ. of Wyoming, Laramie, WY (United States). Dept. of Geology and Geophysics
2. Queen's Univ., Kingston, Ontario (Canada). Geological Sciences

In the Salmon River Arch, a ca. 1,365 Ma rapikivi granite intrudes the Proterozoic Yellow Jacket Formation, which is commonly correlated with the basal Belt-Purcell Supergroup. The contact aureole of the granite contains andalusite and overprints greenschist-facies burial metamorphism in the undeformed sedimentary strata. To the north, the granite intrudes amphibolite-facies, migmatitic paragneiss and a mafic igneous complex. Textures within the migmatites attest to deformation during partial melting. Preliminary U-Pb zircon data from a quartz diorite that intrudes the Yellowjacket sediments yield an age of ca. 1,445 Ma. This is consistent with zircon ages from the Crossport C and Moyie sills in northern Idaho and southern BC that constrain the basal Belt Supergroup to be older than 1,440 Ma. U-Pb zircon data from an amphibolitized mafic dike within the mafic igneous complex along the Salmon River are nearly concordant and yield Pb/Pb ages of ca. 1,377 Ma. The zircons exhibit skeletal, magmatic morphologies and the age is interpreted to be the time of primary crystallization. This age is slightly older than the age of the rapikivi granite and overlaps with the U-Pb zircon age of leucosomes in the migmatites. Thus, bimodal magmatism and partial melting occurred ca. 1,370 Ma. Deformation accompanied these events, but was concentrated in the deeper level, high-grade rocks. These processes are syn-depositional, based on age constraints from the intrusive quartz diorite. The authors envision that burial metamorphism, deformation, partial melting mafic magmatism and granite emplacement occurred during extensional deformation in the base of the Yellowjacket basin.

• OSTI ID: 5421776
• Report Number(s): CONF-9305259-; CODEN: GAAPBC
• Journal Information: Geological Society of America, Abstracts with Programs; (United States), Vol. 25:5; Conference: 89. annual meeting of the Cordilleran Section and the 46th annual meeting of the Rocky Mountain Section of the Geological Society of America (GSA), Reno, NV (United States), 19-21 May 1993; ISSN 0016-7592
• Country of Publication: United States
• Language: English

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58 GEOSCIENCES
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PETROGENESIS
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PLUTONIC ROCKS
ZIRCON
DEFORMATION
GEOLOGIC MODELS
LEAD ISOTOPES
MAGMATISM
METAMORPHISM
PRECAMBRIAN ERA
URANIUM ISOTOPES
ACTINIDE ISOTOPES
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USA
580000* - Geosciences