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Detrital Zircon Provenance of Neoproterozoic to Cambrian Successions: Resolving Continental Configurations
RODINIA, GONDWANA AND ASIA
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Detrital Zircon Provenance of Neoproterozoic to Cambrian Successions: Resolving Continental Configurations Marilyn B. Vogell, Joseph L. Wooden2, Edmund Stump3and Michael 0.Mc Williams’ Department of Geological and Environmental Sciences, Stanford University, Stanford, C A 94305-2115, U S A US Geological Survey, Menlo Park, C A , 94025, U S A Department of Geological Sciences, Arizona State University, Tempe, A Z 85287-1404, U S A Late Precambrian to Cambrian sedimentary basins positioned along rift margins offer diverse information on the depositional setting, sediment transport and source terrains involved in the Rodinia to Gondwana transition. Detrital zircons from these successions offer a unique information-bearing variable that can help resolve the relative positioning of cratonal blocks in the supercontinent. These age spectra can also be compared to a craton’s geologic history in order to evaluate a given unit’s affinity to local or exotic source areas. SHRIMP age spectra from the Neoproterozoic Beardmore Group in Antarctica derive from source terrains ranging in age from ca. 550 to 1200 Ma. Zircon populations with ages of 600 Ma and 1000 Ma have a strong statistical presence in several samples from the La Gorce Formation of the Beardmore Group, with a minor zircon population of ca. 800 Ma. The youngest detrital grains, which record the Beardmore Group’s maximum age of deposition, suggest that at least some Beardmore Group sediments were deposited after the initiation of plutonism (550 Ma) related to the Early Cambrian Ross Orogeny. Beardmore Group spectra resemble those determined for Early Cambrian sediments of the Adelaide Geosyncline (Ireland et al., 1998), but absent in the Antarctic spectra are grains older than 1200 Ma. Meanwhile Neoproterozoic/Eocambrian clastics from North America’s rift to drift successions show distinctly different provenance signatures. An ascending sampling of one of North America’s most westerly rift to passive margin successions revealed a provenance that matched neither local basement nor Antarctic sources. Known as the Big Bear Group, (Cameron, 1981) this quartzite and phyllite succession is possessed of
distinct Early Proterozoic to Archean material, as we11 as a large population of 1.3-1.5 Ga grains. In addition, the youngest grains found in these rocks date at ca. 900 Ma, showing that the Laurentia margin was isolated from the ca. 600-800 Ma source present in Antarctic sediments. Units analyzed for this study are currently undergoing revision with regards to their correlation to other units and chronostratigraphic position (Goodge et al., 2000; Vogel et al., 2001). Provenance studies aid in reevaluating how, when and where these basins formed, as well as provide a unique test for conjugate margin hypotheses such as SWEAT (Dalziel, 1991).
References Cameron, C.S. (1981) Geology of the Sugarloaf and Delamar mountain areas, San Bernardino mountains, California: PhD Thesis, Massachusetts Institute of Technology, 39913. Dalziel, I.W.D. (1991) Pacific margins of Laurentia and East AntarcticaAustralia as a conjugate rift pair; evidence and implications for an Eocambrian supercontinent. Geology, v. 19, pp. 598-601. Goodge, J.W., Myrow, €? and Williams, I.S. (2000) Age and provenance of the Beardmore group, Antarctica: constraints o n Rodinia supercontinent breakup. Geol. SOC.America, Abstracts with Programs, v. 32, p. 59. Ireland, T.R., Flottmann, T., Fanning, C.M., Gibson, G.M. and Preiss, W.V. (1998) Development of the early Paleozoic Pacific margin of Gondwana from detrital-zircon ages across the Delamerian orogen. Geology, v. 26, pp. 243 -246. Vogel, M.B., Wooden, J.L. and Barth, A.P. (2001) Detrital zircon provenance of Late Precambrian to Early Cambrian sediments from the San Bernadino mountains, CA. Geol. SOC.America, Abstracts with programs, Cordilleran sectional meeting, (in press).
Geologic Nature of Granulite Complex of the Southern Aldan Shield G.M. Vovna Far-Eastern Geological Institute FEB R A S , Vladivostok, Russia The early crust formations of the southern Aldan Shield in the Archaean are represented by deep- seated granulites (the Sutamskaya deep facies) exposed in various tectonic blocks such as the Sutamsky, Zverevsky, Kurultinsky and Dzhugdzhursky. Deep-seated rocks occurring in these blocks are of great interest for solving problems concerning the early crustal evolution of the East Siberian craton. This study examines the protoliths of the Sutamsky block granulite complex in the southern Aldan Shield within the Sutam River basin. Two major formation are ~~
Gondwana Research, V. 4,No. 4,2001
identified here: the lower metabasite-enderbite formation and upper enderbite-gneiss. The metabasite-enderbite formation was derived from volcanic rocks (including subvolcanic formations) of calc-alkali series containing basalts, andesites, dacites, rhyodacites and andesites. Initial volcanites of this series are distinguished as basalt- andesite- dacite association. Minor part of the formation (
809
Detrital Zircon Provenance of Neoproterozoic to Cambrian Successions: Resolving Continental Configurations Marilyn B. Vogell, Joseph L. Wooden2, Edmund Stump3and Michael 0.Mc Williams’ Department of Geological and Environmental Sciences, Stanford University, Stanford, C A 94305-2115, U S A US Geological Survey, Menlo Park, C A , 94025, U S A Department of Geological Sciences, Arizona State University, Tempe, A Z 85287-1404, U S A Late Precambrian to Cambrian sedimentary basins positioned along rift margins offer diverse information on the depositional setting, sediment transport and source terrains involved in the Rodinia to Gondwana transition. Detrital zircons from these successions offer a unique information-bearing variable that can help resolve the relative positioning of cratonal blocks in the supercontinent. These age spectra can also be compared to a craton’s geologic history in order to evaluate a given unit’s affinity to local or exotic source areas. SHRIMP age spectra from the Neoproterozoic Beardmore Group in Antarctica derive from source terrains ranging in age from ca. 550 to 1200 Ma. Zircon populations with ages of 600 Ma and 1000 Ma have a strong statistical presence in several samples from the La Gorce Formation of the Beardmore Group, with a minor zircon population of ca. 800 Ma. The youngest detrital grains, which record the Beardmore Group’s maximum age of deposition, suggest that at least some Beardmore Group sediments were deposited after the initiation of plutonism (550 Ma) related to the Early Cambrian Ross Orogeny. Beardmore Group spectra resemble those determined for Early Cambrian sediments of the Adelaide Geosyncline (Ireland et al., 1998), but absent in the Antarctic spectra are grains older than 1200 Ma. Meanwhile Neoproterozoic/Eocambrian clastics from North America’s rift to drift successions show distinctly different provenance signatures. An ascending sampling of one of North America’s most westerly rift to passive margin successions revealed a provenance that matched neither local basement nor Antarctic sources. Known as the Big Bear Group, (Cameron, 1981) this quartzite and phyllite succession is possessed of
distinct Early Proterozoic to Archean material, as we11 as a large population of 1.3-1.5 Ga grains. In addition, the youngest grains found in these rocks date at ca. 900 Ma, showing that the Laurentia margin was isolated from the ca. 600-800 Ma source present in Antarctic sediments. Units analyzed for this study are currently undergoing revision with regards to their correlation to other units and chronostratigraphic position (Goodge et al., 2000; Vogel et al., 2001). Provenance studies aid in reevaluating how, when and where these basins formed, as well as provide a unique test for conjugate margin hypotheses such as SWEAT (Dalziel, 1991).
References Cameron, C.S. (1981) Geology of the Sugarloaf and Delamar mountain areas, San Bernardino mountains, California: PhD Thesis, Massachusetts Institute of Technology, 39913. Dalziel, I.W.D. (1991) Pacific margins of Laurentia and East AntarcticaAustralia as a conjugate rift pair; evidence and implications for an Eocambrian supercontinent. Geology, v. 19, pp. 598-601. Goodge, J.W., Myrow, €? and Williams, I.S. (2000) Age and provenance of the Beardmore group, Antarctica: constraints o n Rodinia supercontinent breakup. Geol. SOC.America, Abstracts with Programs, v. 32, p. 59. Ireland, T.R., Flottmann, T., Fanning, C.M., Gibson, G.M. and Preiss, W.V. (1998) Development of the early Paleozoic Pacific margin of Gondwana from detrital-zircon ages across the Delamerian orogen. Geology, v. 26, pp. 243 -246. Vogel, M.B., Wooden, J.L. and Barth, A.P. (2001) Detrital zircon provenance of Late Precambrian to Early Cambrian sediments from the San Bernadino mountains, CA. Geol. SOC.America, Abstracts with programs, Cordilleran sectional meeting, (in press).
Geologic Nature of Granulite Complex of the Southern Aldan Shield G.M. Vovna Far-Eastern Geological Institute FEB R A S , Vladivostok, Russia The early crust formations of the southern Aldan Shield in the Archaean are represented by deep- seated granulites (the Sutamskaya deep facies) exposed in various tectonic blocks such as the Sutamsky, Zverevsky, Kurultinsky and Dzhugdzhursky. Deep-seated rocks occurring in these blocks are of great interest for solving problems concerning the early crustal evolution of the East Siberian craton. This study examines the protoliths of the Sutamsky block granulite complex in the southern Aldan Shield within the Sutam River basin. Two major formation are ~~
Gondwana Research, V. 4,No. 4,2001
identified here: the lower metabasite-enderbite formation and upper enderbite-gneiss. The metabasite-enderbite formation was derived from volcanic rocks (including subvolcanic formations) of calc-alkali series containing basalts, andesites, dacites, rhyodacites and andesites. Initial volcanites of this series are distinguished as basalt- andesite- dacite association. Minor part of the formation (