气候变化领域集成服务门户(CCPortal): Zircon and monazite geochronology in the Palmer zone of transpression, south-central New England, USA: Constraints on timing of deformation, high-grade metamorphism, and lithospheric foundering during late Paleozoic oblique collision in the Northern Appalachian orogen

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DOI	10.1130/B35744.1
	Zircon and monazite geochronology in the Palmer zone of transpression, south-central New England, USA: Constraints on timing of deformation, high-grade metamorphism, and lithospheric foundering during late Paleozoic oblique collision in the Northern Appalachian orogen
	Moecher D.P.; McCulla J.K.; Massey M.A.
发表日期	2021
ISSN	167606
起始页码	1021
结束页码	1038
卷号	133 期号:2021-05-06
英文摘要	Middle to late Paleozoic high-angle (45°) oblique convergence between Laurentia and composite Avalon terranes resulted in crustal shortening of -5:1 across the Central Maine and Bronson Hill zones of the southern New England Appalachians (USA). The Palmer zone of transpression illustrates the midcrustal expression of magmatism, metamorphism, and ductile deformation that developed in response to oblique convergence in the apparent absence of subduction. Secondary ion mass spectrometry zircon U-Pb and monazite Th-Pb ages, supplemented by zircon laser-ablation-inductively coupled plasma-single-collector mass spectrometry U-Pb ages, expand the geochronology constraining the evolution of the Palmer zone of transpression system and potential models for transcurrent collisional tectonics. Ordovician, Silurian, and Early Devonian plutons, and regional high-grade metapelitic country rocks that comprise the pre-transpressional crustal infrastructure are the same age as lithologic equivalents to the north and northeast along the orogen that did not experience high-angle oblique convergence. All plutons within the Palmer zone of transpression and adjoining areas were deformed (flattened, boudinaged, attenuated, folded, and/or duc-tilely sheared) by the regional transpression system. The most widespread magmatic event in the study area, which is not observed elsewhere in the Northern Appalachians, is intrusion of a diorite-tonalite suite at 370360 Ma, the oldest rocks of which contain granulite-facies mineral assemblages and all of which are deformed. Leucopegma-tites that intrude pelitic paragneisses, which likely formed in response to high-grade metamorphism and which are all deformed, are 370-355 Ma in age. All metapelitic paragneisses contain foliations and linea-tions that are synkinematic with retrograde garnet + K-feldspar sillimanite + biotite assemblages and fabrics that formed during vertical and lateral crustal escape in response to extreme shortening. Contemporaneous diorite-tonalite magmatism and regional high-grade metamorphism are interpreted to reflect regional-scale heating of the crust preceding inception of the transpressional system. Transpressional deformation of both plutons and paragneisses indicates shortening commenced after crustal thermal conditions peaked (ca. 355 Ma). Monazite in paragneiss, the formation of which in most samples is linked texturally to formation of transpressional fabrics, yielded a continuum of Th-Pb ages of ca. 360-330 Ma, indicating transpression continued after peak thermal conditions. The extreme crustal shortening of the Bronson Hill and Central Maine zones from Maine to southern New England, pre-transpressional magmatism, and high-grade metamorphism overprint an Acadian (ca. 400-370 Ma) magmatic-metamorphic infrastructure that occurred in the absence of subduction. The transpressional system exhibits all predicted thermal, magmatic, deformation, metamorphic, and exhumation/erosion characteristics of mantle lithospheric foundering (delamination, detachment, or drip) in response to extreme lithospheric shortening and vertical stretching at ca. 375-370 Ma, leading to advection of heat to the lower con- tinental crust and attendant magmatic and metamorphic responses over the time span 370-355 Ma. © 2021 Geological Society of America. All Rights Reserved.
语种	英语
来源期刊	Bulletin of the Geological Society of America
文献类型	期刊论文
条目标识符	http://gcip.llas.ac.cn/handle/2XKMVOVA/184674
作者单位	Department of Earth and Environmental Sciences, University of Kentucky, Lexington, Kentucky 40506, United States; Pioneer Natural Resources, Irving, Texas 75038, United States; Kentucky Geological Survey, Lexington, Kentucky 40506, United States
推荐引用方式 GB/T 7714	Moecher D.P.,McCulla J.K.,Massey M.A.. Zircon and monazite geochronology in the Palmer zone of transpression, south-central New England, USA: Constraints on timing of deformation, high-grade metamorphism, and lithospheric foundering during late Paleozoic oblique collision in the Northern Appalachian orogen[J],2021,133(2021-05-06).
APA	Moecher D.P.,McCulla J.K.,&Massey M.A..(2021).Zircon and monazite geochronology in the Palmer zone of transpression, south-central New England, USA: Constraints on timing of deformation, high-grade metamorphism, and lithospheric foundering during late Paleozoic oblique collision in the Northern Appalachian orogen.Bulletin of the Geological Society of America,133(2021-05-06).
MLA	Moecher D.P.,et al."Zircon and monazite geochronology in the Palmer zone of transpression, south-central New England, USA: Constraints on timing of deformation, high-grade metamorphism, and lithospheric foundering during late Paleozoic oblique collision in the Northern Appalachian orogen".Bulletin of the Geological Society of America 133.2021-05-06(2021).