TY - JOUR
T1 - Timing of Grenville magmatism in the southern Blue Ridge, North Carolina, USA
T2 - New in situ zircon U-Pb geochronology and implications for timing of Rodinian orogenesis in eastern Laurentia
AU - Makovsky, Kyle
AU - Samson, Scott D.
AU - Moecher, David P.
AU - Amidon, William
N1 - Funding Information:
1. Pre-Elzevirian magmatism is supported by the 1283–1250 Ma Earlies Gap granitoid gneiss (map units Yepg and Yegpg) and by zircon xenocrysts within Earlies Gap granitoid gneiss (Yepg), Fines Creek gneiss (Ymg), and Max Patch granite (Ym).
Funding Information:
This research was funded by NSF EAR 1447611 to Samson, NSF EAR- 1447605 and NSF I&F EAR-1551342 to Moecher, and a Geological Society of America (GSA) Graduate Research Grant to the lead author. The funding sources did not have any interference in the study design, collection of analyses, in writing of the report, or the interpretation of the data. Jay Thomas is acknowledged for his help with teaching the lead author how to make “the best” zircon grain mounts.
Publisher Copyright:
© 2021 Elsevier B.V.
PY - 2021/9/1
Y1 - 2021/9/1
N2 - 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).
AB - 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).
KW - Blue Ridge
KW - French Broad Massif
KW - Grenville
KW - Southern Appalachians
KW - Zircon U-Pb
UR - http://www.scopus.com/inward/record.url?scp=85111517378&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=85111517378&partnerID=8YFLogxK
U2 - 10.1016/j.precamres.2021.106313
DO - 10.1016/j.precamres.2021.106313
M3 - Article
AN - SCOPUS:85111517378
SN - 0301-9268
VL - 363
JO - Precambrian Research
JF - Precambrian Research
M1 - 106313
ER -