The origin and tectonic significance of the mafic-ultramafic association in the central Virginia Blue Ridge post-Grenville cover sequence

• Main Author: Thompson, Wendi R.
• Other Authors: Geological Sciences
• Format: Others
• Language: en
• Published: Virginia Tech 2014
• Subjects: LD5655.V855 1996.T468
• Online Access: http://hdl.handle.net/10919/44509; http://scholar.lib.vt.edu/theses/available/etd-08292008-063748/

The question of whether the mafic and ultramafic rocks of the central Virginia Blue Ridge are part of a Late Proterozoic to Ordovician ophiolite-bearing sequence or part of an intrusive-extrusive sequence related to the Late Proterozoic Iapetan rifting has major implications for Appalachian tectonic models. Current models consider most of the Blue Ridge cover sequence to be ophiolitic mélange that was obducted onto Laurentia, thus implying a suture or terrane boundary is associated with the rocks. Detailed field mapping and petrography of three typical mafic-ultramafic complexes in the central Virginia Blue Ridge (the Catfish, Flat Creek, and Schuyler complexes) indicate that these bodies do not show characteristics that resemble ophiolites. The three complexes are broadly conformable with stratigraphic layering, and the Lynchburg Group host strata form a continuous and conformable stratigraphic sequence unbroken by faults and without evidence of mélange. Contacts between the mafic-ultramafic bodies and the host rocks are sharp and show no strong evidence for faulting or other disturbances. Internal contact relations and the presence of autoliths indicate that these bodies were derived from multiple injection of a fractionating basaltic magma. The characteristics of the Catfish, Flat Creek, and Schuyler complexes confirm that the mafic-ultramafic association is an intrusive sequence rocks intimately related to the Late Proterozoic Iapetan rifting. The rocks are not part of a Late Proterozoic to Ordovician ophiolite sequence or mélange. Therefore, there are no sutures or terrane boundaries in the central Virginia Blue Ridge. === Master of Science