New insights into the crustal architecture and tectonic evolution of the Eastern Gulf of Mexico.

Author(s):  
Athanasia Vasileiou ◽  
Mohamed Gouiza ◽  
Estelle Mortimer ◽  
Douglas Paton ◽  
Aleece Nanfito ◽  
...  

<p>The Gulf of Mexico is an intraplate oceanic basin where rifting started in the Late Triassic, leading to drifting by Middle Jurassic and ensuing oceanic accretion, which ceased by the Early Cretaceous. Its tectonic evolution encompasses multiple rifting phases dominated by orthogonal extension, major strike-slip structures, transtensional basins, variable magmatism, and salt deposition. This complex tectonic history is captured in the rifted margins of the Gulf of Mexico, especially along the eastern part of the basin; where considerable debate remains regarding the crustal configuration and tectonic evolution.</p><p>This study presents new insights into the crustal types and an updated tectonic framework for the Florida margin. An integrated analysis of seismic, gravity, and magnetic data allows us to characterise the continental crust, which shows wide zones of hyperextension that we relate to pull-apart basins, magmatic underplating, seaward dipping reflection (SDR) packages, and a narrow zone of exhumed mantle. In addition, we identified NW-SE trending sinistral strike-slip faults altering the typical crustal configuration expected in a rifted margin.</p><p>Our results suggest the need for a new plate model of the Florida margin at the Eastern Gulf of Mexico that invokes the polyphase rifting, accounts for the Yucatan’s block counter-clockwise rotation, explains the increase in magma supply, and captures the influence of strike-slip faults on the crustal boundaries and the magmatic budget.    </p>

1996 ◽  
Vol 33 (5) ◽  
pp. 800-810 ◽  
Author(s):  
Edward D. Ghent ◽  
Philippe Erdmer ◽  
Douglas A. Archibald ◽  
Mavis Z. Stout

A blueschist and eclogite terrane is associated with one of the largest faults in the Canadian Cordilleran Orogen, the Pinchi fault. Blueschists (in situ) and retrogressed eclogite blocks occur along the Pinchi fault zone near 54°30'N and 124°W. Critical blueschist facies mineral assemblages include lawsonite–glaucophane, jadeite–lawsonite–glaucophane–quartz, and aragonite. White mica 40Ar/39Ar spectra on blueschist and eclogite yield ages in the range 221.8 ± 1.9 to 223.5 ± 1.7 Ma, establishing a direct link between the blueschists and eclogites. Preservation of aragonite sets rigid constraints on the pressure–temperature–fluid–time conditions of unroofing. K–Ar dates indicate that this is some of the oldest documented metamorphic aragonite. Comparison with computed petrogenetic grids suggests that metamorphic temperatures were in the range 200–300 °C, with pressures greater than 8–10 kbar (1 kbar = 100 MPa). Unroofing likely occurred during collision of the Cache Creek terrane with Quesnellia in the Late Triassic to Middle Jurassic. The fault was initiated as a plate boundary and was active as late as Eocene time as a strike-slip zone. The Pinchi blueschist terrane is similar to others in the North American Cordillera and highlights a tectonic regime of repeated blueschist metamorphism and rapid unroofing along many parts of the western margin of North America in the early Mesozoic.


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