Seismic Evidence for Metamorphic Densification of the Lower Continental Crust in Eastern North America

Li, Cong1,2; Hibbard, Leon1; Gao, Haiying1; Williams, Michael L.1

2023-06-01

10.1029/2023JB026602

JOURNAL OF GEOPHYSICAL RESEARCH-SOLID EARTH   影响因子和分区

2169-9313

2169-9356

The composition of the lower continental crust, as well as its formation, growth, and evolution, remains a fundamental subject to be understood. In this study, we carry out a comparative and integrative analysis of seismic tomographic models, teleseismic receiver function results, and Airy isostasy in order to investigate the properties of the lower continental crust in eastern North America. We extract the depths for Vs of 4.0 km/s, 4.2 km/s, and 4.5 km/s from three selected tomographic models and calculate the differences between the Vs depth contours and the Moho depth defined by receiver functions. We then calculate the Airy isostatic Moho depth and its misfit with the receiver-function-defined Moho. Our analysis reveals three key features: (a) the deepening of the Vs depth contours and the strong negative Airy misfit within the U.S. Grenville Province; (b) a seismically faster-than-average and compositionally denser-than-average lowermost crust in the eastern North American Craton and the Grenville Province; and (c) the thickest, seismically fastest, and densest lowermost crust beneath the southern Grenville Front, the southern Grenville-Appalachian boundary, and the U.S.-Canada national border. We suggest that the lower crust of the craton and the Grenville Province has densified through garnet-forming metamorphic reactions during and after orogenesis, contributing to the widely distributed fast-velocity layer. The lower crust beneath the tectonic boundaries could have experienced more extensive garnet growth during orogenesis and emplacement of mafic magma. This study provides new constraints on the seismic and compositional properties of the lower crust in eastern North America.

continental crust eastern north America crustal evolution fast-velocity layer garnet growth metamorphism

SCI

英语

NI论文

通讯

U.S. National Science Foundation[EAR-1930014]

Geochemistry & Geophysics

Geochemistry & Geophysics

WOS:001006569700001

AMER GEOPHYSICAL UNION

GEOSCIENCES

Web of Science

1.Univ Massachusetts Amherst, Dept Earth Geog & Climate Sci, Amherst, MA 01003 USA
2.Southern Univ Sci & Technol, Dept Earth & Space Sci, Shenzhen, Peoples R China

Li, Cong,Hibbard, Leon,Gao, Haiying,et al. Seismic Evidence for Metamorphic Densification of the Lower Continental Crust in Eastern North America[J]. JOURNAL OF GEOPHYSICAL RESEARCH-SOLID EARTH,2023,128(6).

Li, Cong,Hibbard, Leon,Gao, Haiying,&Williams, Michael L..(2023).Seismic Evidence for Metamorphic Densification of the Lower Continental Crust in Eastern North America.JOURNAL OF GEOPHYSICAL RESEARCH-SOLID EARTH,128(6).

Li, Cong,et al."Seismic Evidence for Metamorphic Densification of the Lower Continental Crust in Eastern North America".JOURNAL OF GEOPHYSICAL RESEARCH-SOLID EARTH 128.6(2023).