Isotopic structure and tectonics of the central Transantarctic Mountains

Journal Article · Thu May 10 04:00:00 EDT 1990 · Journal of Geophysical Research; (United States)

DOI:https://doi.org/10.1029/JB095iB05p06647· OSTI ID:5014861

Borg, S G; DePaolo, D J; Smith, B M ^[1]

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1. Univ. of California, Berkeley (United States) Lawrence Berkeley Lab., Berkeley, CA (United States)

Regional patterns of Nd, Sr, and O isotopic ratios of {approximately} 500 Ma granite rocks are used to identify the ages and areal extents of three crustal provinces in the central Transantarctic Mountains. One of the provinces is the edge of the East Antarctic Craton, which isotopic analyses show is composed of Archean rocks thrust over Proterozoic rocks. The other two provinces compose the Beardmore microcontinent. Evidence for a former ocean basin between the Beardmore microcontinent and East Antarctica is provided by basalt and gabbro of mid-ocean ridge character, dated by Sm-Nd at {approximately} 760 Ma. The granitic rocks formed over a westward-dipping subduction zone that was active at {approximately} 500 Ma. The isotopic provinces correspond to differences in age and composition of the middle and lower crust at the time of formation of the granite magmas. The boundaries of the isotopic provinces also correspond to discontinuities in provenance, lithology, structural style, and grade of metamorphism of prebatholithic metasedimentary rocks. The isotopic data indicate that the granite magmas were formed mostly by crustal anatexis in the areas west of the Shackleton Glacier. The tectonic history deduced for the Gondwana margin, as represented in the central Transantarctic Mountains, began with deposition of sediments on an Atlantic-type rifted margin at {approximately} 760 Ma. The Beardmore microcontinent was most likely accreted in association with folding of the clastic sedimentary rocks before middle Early Cambrian time (550 Ma). Carbonate sedimentation and volcanism along the eastern margin of the Beardmore microcontinent commenced in Cambrian time. Folding and metamorphism of all older units occurred in late Cambrian time followed by emplacement of granite rocks at {approximately} 500 Ma.

• OSTI ID: 5014861
• Journal Information: Journal of Geophysical Research; (United States), Journal Name: Journal of Geophysical Research; (United States) Vol. 95:B5; ISSN 0148-0227; ISSN JGREA
• Country of Publication: United States
• Language: English

Related Subjects

58 GEOSCIENCES
580000* -- Geosciences
AGE ESTIMATION
ALKALINE EARTH ISOTOPES
ANTARCTIC REGIONS
ANTARCTICA
BASALT
BETA DECAY RADIOISOTOPES
CARBONATE ROCKS
CONTINENTAL CRUST
DEPOSITION
EARTH CRUST
ELECTRON CAPTURE RADIOISOTOPES
EVEN-EVEN NUCLEI
EVEN-ODD NUCLEI
GABBROS
GEOLOGIC FORMATIONS
GEOLOGIC HISTORY
GEOLOGIC STRUCTURES
GLACIERS
GRANITES
HOURS LIVING RADIOISOTOPES
IGNEOUS ROCKS
INTERMEDIATE MASS NUCLEI
ISOMERIC TRANSITION ISOTOPES
ISOTOPE RATIO
ISOTOPES
LIGHT NUCLEI
LITHOLOGY
MAGMA
METAMORPHISM
MOUNTAINS
NEODYMIUM ISOTOPES
NUCLEI
OXYGEN 18
OXYGEN ISOTOPES
PLUTONIC ROCKS
POLAR REGIONS
RADIOISOTOPES
RARE EARTH ISOTOPES
ROCKS
SAMARIUM ISOTOPES
SEDIMENTARY BASINS
SEDIMENTARY ROCKS
SEDIMENTS
STABLE ISOTOPES
STRONTIUM 86
STRONTIUM 87
STRONTIUM ISOTOPES
SUBDUCTION ZONES
TECTONICS
VOLCANIC ROCKS
VOLCANISM