Timing of Grenville magmatism in the southern Blue Ridge, North Carolina, USA: New in situ zircon U-Pb geochronology and implications for timing of Rodinian orogenesis in eastern Laurentia

Kyle Makovsky, Scott D. Samson, David P. Moecher, William Amidon

Research output: Contribution to journalArticlepeer-review

Abstract

Mesoproterozoic metaplutonic rocks from the southern French Broad massif in southwestern North Carolina preserve Grenville magmatic and metamorphic ages (1.28–1.0 Ga). New in-situ zircon U-Pb measurements from eight basement lithologies, obtained by laser ablation and ion-probe techniques, delineate Elzevirian (1283–1250 Ma), Shawinigan (1191–1126 Ma), and Ottawan (1034–1008 Ma) magmatism and metamorphism. Magmatism produced dominantly calc-alkaline plutons with normative compositions of quartz diorite, quartz monzodiorite, granodiorite, and monzogranite. The majority of magmatism in the field area occurred between ca. 1190 and 1125 Ma, a period correlative to the Shawinigan phase of the Grenville orogeny. Syn- to post-emplacement metamorphism of these units is evidenced by complex zircon U-Pb systematics in all Shawinigan age plutons. Ottawan magmatism, expressed by emplacement of the Max Patch granite and protoliths of the Earlies Gap granitoid gneiss, is less voluminous than Shawinigan magmatism; a difference that mirrors their relative proportions elsewhere in the orogen. Ottawan metamorphism is recorded by growth of new zircon rims around magmatic core domains in several samples and spans a period of ca. 25 m.y. from ca. 1035 to 1010 Ma. The timing of the older and younger magmatic suites from the southern French Broad massif correlate to well-established times of Shawinigan and Ottawan magmatism and metamorphism in other Grenville-age terranes within the U.S. (e.g., Appalachian inliers, Adirondacks).

Original languageEnglish (US)
Article number106313
JournalPrecambrian Research
Volume363
DOIs
StatePublished - Sep 1 2021

Keywords

  • Blue Ridge
  • French Broad Massif
  • Grenville
  • Southern Appalachians
  • Zircon U-Pb

ASJC Scopus subject areas

  • Geology
  • Geochemistry and Petrology

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