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Journal Article
Journal: Lithosphere
Published: 11 October 2017
Lithosphere (2017) 9 (6): 953-975.
...Harold H. Stowell; J.J. Schwartz; K.A. Klepeis; C. Hout; A.J. Tulloch; A. Koenig AbstractSm-Nd garnet and U-Pb zircon ages for eclogite and granulite from the Breaksea Orthogneiss provide a detailed chronology for pluton emplacement and subsequent thermal history of the lower arc crust exposed...
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Journal Article
Journal: Geosphere
Published: 25 September 2017
Geosphere (2017) 13 (6): 1949-1972.
... of the Bad River granite in the southwestern Grenville Front tectonic zone in Ontario, Canada. The granite is bounded on both sides by older orthogneiss (ca. 1720 Ma igneous crystallization age). Zircon U-Pb ages indicate that the granite crystallized from a magma at ca. 1465 Ma, with metamorphic growth...
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Series: GSA Field Guide
Published: 01 January 2016
DOI: 10.1130/2016.0041(09)
EISBN: 9780813756417
..., similar to where Archean basement is exposed in the northern portion of the complex near Priest River, Idaho. At Cougar Gulch, the basement rocks are composed of a variety of granitic orthogneisses and amphibolite, which are unconformably overlain by a graphite-bearing orthoquartzite. The orthoquartzite...
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Series: GSA Memoirs
Published: 01 September 2010
DOI: 10.1130/2010.1206(08)
... by a dominant D 2 migmatitic layering and are likely Taconic. U-Pb zircon crystallization ages of felsic orthogneiss and tonalite, syntectonic with respect to the formation of S 2 , and a biotite quartz diorite that crosscuts level 2 paragneiss are 437 ± 4 Ma, 434 ± 4 Ma, and 437 ± 4 Ma, respectively. Level...
Series: GSA Memoirs
Published: 01 September 2010
DOI: 10.1130/2010.1206(31)
... Geologic mapping of Mesoproterozoic lithologies and foliations, and sensitive high-resolution ion microprobe (SHRIMP) U-Pb crystallization ages of 43 samples of orthogneisses and metagranitoids from the northern Blue Ridge establish new subdivisions: group 1 (1183–1144 Ma), group 2 (1143–1111...
Series: GSA Special Papers
Published: 01 January 2008
DOI: 10.1130/2008.2440(09)
... geochemical data for suites of granitic rocks, in order to establish a testable model for the geodynamic setting and the tectonomagmatic evolution of the Late Archean crust. The geochemistry of TTG orthogneiss and plutons are correlated, petrogenetically and temporally, with the published data...
Series: GSA Special Papers
Published: 01 January 2007
DOI: 10.1130/2007.2434(07)
... for the orthogneiss of Little Lake (A) and the Sacatar Quartz Diorite (B). Figure 6. Tera and Wasserburg (1972) total Pb projections of SHRIMP-RG data for rocks from the southern Sierra Nevada batholith. Analyses represented by open symbols were not included in regressions because they were...
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Series: GSA Special Papers
Published: 01 January 2007
DOI: 10.1130/2007.2423(09)
... Ca. 500 Ma orthogneisses and bimodal suites are widespread along the northern part of the Bohemian Massif (central European Variscides) and are interpreted to document intense magmatism during a continental break-up episode along the northern periphery of Gondwana. Based on geological setting...
Series: GSA Special Papers
Published: 01 January 2006
DOI: 10.1130/2006.2405(06)
...-microprobe study in the Saglek block, Nain Province, northern Labrador, identical ages for magmatism of 3.73 Ga were reported for both amphibolite- and granulite-grade orthogneisses, based on the oldest 207 Pb/ 206 Pb ages in two and three grains, respectively ( Schiøtte et al., 1989 ). Here we present...
Series: GSA Special Papers
Published: 01 January 1992
DOI: 10.1130/SPE272-p291
... Granites of the Batholith of Central Patagonia were emplaced into late Precambrian metamorphic basement rocks and Palaeozoic orthogneisses (here dated by Rb–Sr whole-rock errorchrons at 346 ±35 Ma and 267 ±27 Ma), and are in fault-contact with younger volcanic rocks, mostly andesites. Two main...
Series: GSA Special Papers
Published: 01 January 1990
DOI: 10.1130/SPE241-p9
... quartz-diorites to granites, have high LIL/HFS element ratios, and their analyses all fall in the volcanic arc granite field when plotted on granite discrimination diagrams. The Paleozoic group comprises orthogneisses that have undergone high-grade metamorphism. The Jurassic group is variably foliated...
Series: GSA Special Papers
Published: 01 January 1990
DOI: 10.1130/SPE245-p187
... amphibolite and calc-silicate xenoliths, from a massive structure lacking compositional layering, and from kilometer-scale chemical zoning or homogeneity. The identification of some units as lithodemic orthogneisses indicates that intrusion as well as extrusion led to the lithologic sequences in the Avalon...
Series: GSA Special Papers
Published: 01 January 1990
DOI: 10.1130/SPE245-p209
... orthogneiss. Rocks originally mapped as Brimfield Formation (Merrimack terrane) west of Old Saybrook are shown to correlate with the Middletown Formation of the Bronson Hill terrane. This new correlation makes all plagioclase gneisses of the Killingworth dome isolated from rocks of other terranes...
Series: GSA Special Papers
Published: 01 January 1989
DOI: 10.1130/SPE232-p47
...-hornblende-K-feldspar orthogneiss) occurred during middle to Late Cretaceous time. Pegmatite dikes dated as 70 to 58 Ma (K-Ar-mica) cut the gneisses. ...