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Armienti, Pietro; Tamponi, M; Pompilio, Massimo (2001): Geochemistry of minerals in CRP sediment cores from the Ross Sea, Antarctica. PANGAEA,, Supplement to: Armienti, P et al. (2001): Sand provenance from major and trace element analyses of bulk rock and sand grains from CRP-2/2A, Victoria Land Basin, Antarctica. Terra Antartica, 8(4), 569-582, hdl:10013/epic.28219.d001

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Sixty-four volcanic chists, sandstones and tephras between 5.95 and 618.19 meters below sea floor (mbsf) in the Cape Roberts Project cores 2 and 2A cores (CRP-2/2A) were examined for Cenozoic and Mesozoic volcanic components, using optical and Scanning Electron Microscopy. Minerals and glass shards in a selection of samples were analysed by electron microprobe fined with an EDAX detector. Laser-Ablation ICP-Mass-Spectrometry (ICP-MS) was used to determine rare earth elements and 14 additional trace elements in glass shards, pyroxenes and feldspars in order to pin-point the onset of McMurdo Volcanic Group (MVG) activity in the stratigraphic column. Pumices in tephra layers of peralkaline phonolite composition in Unit 7.2 -between 108 and 114 mbsf - were also analysed for trace elements by ICP-MS. This tephra unit is not reworked and its isotopic age (21.44 ± 0.05 Ma) is the age of deposition. The height of the eruptive column responsible for the deposition of the tephra was probably less than 8 km; the source was local, probably within 30 km from the drill site. Phonolite of unit 7.2 of CRP-2/2A has no direct petrogenetic relation with the peralkaline trachyte in the tephra-enriched layer of CRP-1 at 116.55 mbsf.
Volcanic clasts and sand grains (glass shards, aegirine-augite, anorthoclase) related to Cenozoic activity of MVG were observed only starting from Unit 9.8, where they are dated at 24.22 ± 0.06 Ma at c. 280 mbsf. In this unit the lowest- occurring basaltic glass shard is found at 297.54 mbsf. Sampled McMurdo volcanics are generally vesicular and vary in composition from alkali basalt to trachyte and peralkaline phonolite. By contrast, below 320 mbsf, aphyric or slightly-porphyritic volcanic clasts become more abundant but they are all non-vesiculated, pigeconite and ilmenite-bearing basalts and dolerite of tholeiitic affinity. These rocks are considered to be related to lava flows and associated intrusions of Jurassic age (Kirkpatrick basalts and Ferrar dolerite).
As in CRP-1, McMurdo volcanics appear to derive from a variety of lithologics. Besides glaciers, a dominant role of wind transportation from exposed volcanic rocks may be inferred from the contemporary occurrence of glass shards of different compositions at depths above 297.54 mbsf. These data confirm that the onset of magmatic activity in southern Victoria Land is considerably delayed (by about 24 Ma) with respect to northern Victoria Land.
Median Latitude: -77.005992 * Median Longitude: 163.719180 * South-bound Latitude: -77.006000 * West-bound Longitude: 163.719000 * North-bound Latitude: -77.005980 * East-bound Longitude: 163.719450
Date/Time Start: 1998-10-16T07:30:00 * Date/Time End: 1999-11-19T00:00:00
CRP-2A (14.2 km at 096° true from Cape Roberts) * Latitude: -77.005980 * Longitude: 163.719450 * Date/Time Start: 1998-10-16T07:30:00 * Date/Time End: 1998-11-25T14:20:00 * Elevation: -177.9 m * Recovery: 624 m * Location: off Cape Roberts, Ross Sea, Antarctica * Campaign: CRP-2 * Basis: Sampling/drilling from ice * Method/Device: Core wireline system (CWS) * Comment: 921 m at 284° from CRP-1. Sea-ice thickness: 2.0 m (1 Oct) to 2.2 m (23 Nov). Sea riser embedded to 13.03 mbsf. Lateral ice movement: 9.87 m to east from 17 Oct to 23 Nov. HQ core to 199.31 mbsf. NQ core to 624.15 mbsf. 13.03 to 45.97 mbsf, 11.29 m (34%) partially following CRP-2. 45.07 to 624.15 mbsf, 548.67 m (95%) new hole. Deepest core-lithology: hard sandy siltstone. Deepest core-age: earliest Oligocene (ca. 33 Ma on diatoms, nannofossils and dinoflagellates)
CRP-3 * Latitude: -77.006000 * Longitude: 163.719000 * Date/Time Start: 1999-10-09T00:00:00 * Date/Time End: 1999-11-19T00:00:00 * Elevation: -295.0 m * Penetration: 939 m * Recovery: 936 m * Location: Ross Sea * Campaign: CRP-3 * Basis: Sampling/drilling from ice * Method/Device: Core wireline system (CWS) * Comment: 11.76 km at 76° true from Cape Roberts, 2.04 km at 225° true from CRP-2. Fast ice thickness: 2.0 to 2.2 m. Sea rise embedded to 9.55 mbsf. Lateral ice movement from spudding 5.0 m to 82° true. HQ core to 345.85 mbsf. NQ core to 939.42 mbsf. Core recovery 97%. Phase 1 logging to 345 mbsf, Phase 2 logging to 773 mbsf, Phase 3 logging to 918 mbsf. Deepest Cenozoic lithology and depth: sandstone breccia from 822.87 to 823.11 mbsf. Age of oldest Cenozoic strata: earliest Oligocene or latest Eocene. Deepest core lithology and depth: light red-brown quartz-cemented quartz sandstone to 939.42 mbsf. Age of bedrock: (mid?) Devonian.
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