Synthesis of Early and Middle Proterozoic orogenies in the southwest

Conference · Mon Feb 01 04:00:00 EST 1993 · Geological Society of America, Abstracts with Programs; (United States)

OSTI ID:5976683

Karlstrom, K E ^[1]

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1. Univ. of New Mexico, Albuquerque, NM (United States). Dept. of Geology

Accretion of juvenile crust from 1.8 (Colorado) to 1.72 (Arizona) was accompanied by formation, evolution, and assembly of oceanic island arcs in an Indonesian-style orogenic belt. 2.5--2.0 Ga crust formed basement for arcs in the Mojave Province. The Hualapai block marks a zone where arcs were built across the transition from 2.5--2.0 Ga (NW) to juvenile 1.75--1.72 Ga crust (SE). Early NW-striking low-angle foliations formed between 1.74--1.72 Ga and record arc accretion and outboard collisions. Sutures and major transcurrent boundaries between arcs terranes remain cryptic because of 1.7--1.69 Ga crustal shortening that records welding of terranes to Laurentia. 1.7 Ga quartzite-rhyolite sections from a belt parallel to the southern extent of 1.8--1.72 Ga crust and were syntectonic craton margin and intracratonic basins. Depositions of 1.65 Ga quartzite-rhyolite sections took place during the collision of the Mazatzal province. A major boundary between crustal provinces is marked by the Slate Creek shear zone (AZ) - Jemez lineament (NM) although Mazatzal (1.65 Ga) deformation affected the foreland of the Yavapai Province to the north. The Laurasian supercontinent was assembled by 1.6 Ga and tectonism paused in the Southwest (1.6--1.5 Ga) without appreciable uplift of crust. Middle Proterozoic tectonism (1.5--1.3 Ga) has many of the hallmarks of an orogeny rather than anorogeny'. It involved massive lower crustal melting, granitoid plutonism, regional uplift and unroofing of 10-15 km, regional resetting of Rb-Sr and K-Ar isotopic systems, addition of juvenile crust in the Mid-continent, and locally important deformation and metamorphism around plutons and perhaps over large regions. Pluton generation and ascent were strongly controlled by Early Proterozoic lithospheric structure.

• OSTI ID: 5976683
• Report Number(s): CONF-9303212--
• Conference Information: Journal Name: Geological Society of America, Abstracts with Programs; (United States) Journal Volume: 25:1
• Country of Publication: United States
• Language: English

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58 GEOSCIENCES
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CONTINENTAL CRUST
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