Oxygen isotope perspective on Precambrian crustal growth and maturation
In this study the authors contrast insights on Precambrian crustal growth and maturation from radiogenic and oxygen isotope systematics in the Superior (3.0--2.7 Ga) and Grenville (1.3--1.0 Ga) Provinces of the Canadian shield. Oxygen isotope ratios in zircon provide the best evidence of supracrustal input into ancient orogens. Archean Superior Province zircons have relatively low {delta}{sup 18}O values and a limited range (5.7{per_thousand} {+-} 0.6{per_thousand}), while Proterozoic Grenville Province zircons have elevated {delta}{sup 18}O values and a wider range (8.2{per_thousand} {+-} 1.7{per_thousand}). These data reflect fundamental differences in crustal evolution and maturation between the Superior and the Grenville Provinces. In the Grenville Province, radiogenically juvenile supracrustal material with high {delta}{sup 18}O values was buried (or subducted) to the base of the crust within 150 m.y. of initial crust production, causing high magmatic {delta}{sup 18}O values ({delta}{sup 18}O [zircon] {ge} 8{per_thousand}) in anorthosite suite and subsequent plutons. Information about large volumes and rapid recycling of Grenville crust is not accessible from radiogenic isotope data alone. The Grenville data contrast with the restricted {delta}{sup 18}O values of Superior Province magmatism, where subtle ({approximately}1{per_thousand}) elevation in {delta}{sup 18}O occurs only in volumetrically minor, late to postorogenic (sanukitoid) plutons. Differences in sediment {delta}{sup 18}O values between the Superior and Grenville Provinces are predominantly a function of the {delta}{sup 18}O of source materials, rather than differences in chemical maturity or erosion styles. This study shows that zircon is a robust reference mineral to compare igneous processes in rocks that have undergone radically different histories.
- Research Organization:
- Univ. of Wisconsin, Madison, WI (US)
- Sponsoring Organization:
- National Science Foundation (NSF); USDOE
- OSTI ID:
- 20030505
- Journal Information:
- Geology, Vol. 28, Issue 4; Other Information: PBD: Apr 2000; ISSN 0091-7613
- Country of Publication:
- United States
- Language:
- English
Similar Records
Juvenile Middle Proterozoic crust in the Adirondack Highlands, Grenville province, northeastern North America
River Valley pluton, Ontario: A late-Archean/early-Proterozoic anorthositic intrusion in the Grenville Province