Petrology, mineralogy, and geochemistry of the Falkland Plateau basement rocks, Site 330, Deep Sea Drilling Project

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doi: 10.2973/dsdp.proc.36.123.1977
Author(s): Tarney, J.
Author Affiliation(s): Primary:
Univ. Birmingham, Dep. Geol. Sci., Birmingham, United Kingdom
Volume Title: Initial Reports of the Deep Sea Drilling Project
Source: Initial Reports of the Deep Sea Drilling Project, Vol.36, p.893-921. Publisher: Texas A & M University, Ocean Drilling Program, College Station, TX, United States. ISSN: 0080-8334 CODEN: IDSDA6
Note: In English. 25 refs.; illus. incl. tables
Summary: The basement rocks sampled beneath Jurassic sediments in Cores 16 and 17, Site 330, record a long and complex geological history. The oldest rocks present are a series of garnetiferous biotitic gneisses. Petrological and geochemical evidence suggest that these gneisses were mature pelitic, psammitic, and perhaps even arkosic sediments initially, but have suffered prolonged metamorphism and deformation. Thin pegmatic veins were intruded before the main deformation and the metamorphic climax. Emplacement of a later granite pegmatite and related veins was followed by considerable hydrothermal retrogression of the gneisses: replacement of early garnets by chlorite and brown biotites by green to colorless hydrobiotites. A second-generation garnet seems to have developed synchronously with the pegmatite intrusion. The plutonic history was completed by the intrusion of thin basic veins and a microsyenite, but there was later tectonic activity in the form of minor faulting and brecciation. Uplift and erosion exposed the rocks as an undulating Jurassic land surface. This period was characterized by the development of a bedrock calcrete (caliche) in the subaerial zone and replacement of plagioclase by calcite at deeper levels in the core. Burial beneath Jurassic lagoonal sediments preserved the relationships. (Auth.)
Year of Publication: 1977
Research Program: DSDP Deep Sea Drilling Project
Key Words: 05 Petrology, Igneous and Metamorphic; Atlantic Ocean; Basement; Biotite gneiss; Chemical composition; DSDP Site 330; Data; Deep Sea Drilling Project; Falkland Plateau; Genesis; Gneisses; Leg 36; Lower Paleozoic; Metamorphic rocks; Metasedimentary rocks; Mineral assemblages; Paleozoic; Petrology; South Atlantic; Textures
Coordinates: S505500 S505500 W0465300 W0465300
Record ID: 1977040616
Copyright Information: GeoRef, Copyright 2019 American Geosciences Institute. Reference includes data from the Antarctic Bibliography, United States