HR: 1340h
AN: V13E-0597    [Abstracts]
TI: Deformation, Migmatization, and Intrusive Diatexites Along the Contact of the ~~470 Ma Vega Pluton, Helgeland Nappe Complex, North-Central Norway
AU: * Anderson, H
EM: hs.anderson@ttu.edu
AF: Dept. of Geosciences, Texas Tech University 222 Science Building Box 41053, Lubbock, TX 79409-1053 United States
AU: Yoshinobu, A
EM: aaron.yoshinobu@ttu.edu
AF: Dept. of Geosciences, Texas Tech University 222 Science Building Box 41053, Lubbock, TX 79409-1053 United States
AU: Barnes, C
EM: cal.barnes@ttu.edu
AF: Dept. of Geosciences, Texas Tech University 222 Science Building Box 41053, Lubbock, TX 79409-1053 United States
AB: The ~470 Ma (U/Pb) Vega pluton is a large, S-type granodiorite that intrudes folded marble, pelitic, psammitic, and calc-silicate rocks of the Helgeland Nappe Complex (HNC). Emplacement occurred at greather than or equal to 400 MPa based on the presence of kyanite in the contact aureole. The pluton contains a large volume of metasedimentary enclaves including calc-silicate, marble, diatexitic migmatite and probable mafic magmatic enclaves. Mapping coastal exposures of the northwestern contact revealed a ~2 km-wide structural aureole that is characterized by at least two phases of regional deformation (D1-2) and one emplacement-related deformation event (D3). D1 is an early fabric-forming event and is transposed by D2. D2 is defined by NW-trending, moderately plunging isoclines and boudinage with NW-plunging necklines. These structures are folded about E-W-trending, upright, open to tight D3 folds whose axial planes are sub-parallel to the pluton contact. Penetrative D3 structures become less pervasive >2 km northeast of the pluton contact although D3 structures occur outside of the aureole. A composite sheet of diatexite and granodiorite (50-150 m wide) intrudes the calc-silicate rocks 300 m north of the pluton contact. Granodiorite within the sheet is texturally and lithologically comparable to the Vega pluton. The contact between the diatexitic and granodioritic parts of the sheet is gradational over a few meters. Syn-magamtic shear bands and asymmetrical, top to the east dextral folds within the diatexite are parallel to F3 axial planes. Leucogranitic dikes intrude parallel to D3 foliation, locally cross cut D3 folds, and are boudined and folded about F3 axial planes. These observations suggest that emplacement of the diatexite-granodiorite sheet, the leucogranitic dikes and syn-magmatic deformation of these bodies was syn-tectonic with regional D3 deformation. This indicates that D1 and D2 were pre-470 Ma events and likely related to regional migmatization seen elsewhere in the HNC.
DE: 1065 Major and trace element geochemistry
DE: 3625 Petrography, microstructures, and textures
DE: 3642 Intrusive structures and rocks
DE: 8145 Physics of magma and magma bodies
SC: Volcanology, Geochemistry, Petrology [V]
MN: Fall Meeting 2005