Sediment and Rock Samples Recovered from the Challenger Deep, Southern Mariana Trench
Abstract
Sediments collected with push cores during Nereus hybrid-ROV traverses within the trench axis of the Challenger Deep were squeezed onboard ship (R/V Kilo Moana) to extract pore fluids. The squeeze-cakes were analyzed by XRD, SEM, Raman spectroscopy and electron microprobe. The analysis reveals an assemblage of clays, and volcanic ash that contains plagioclase, clino-pyroxene, opaques and, glass. Chlorite is present as are hydrated iron oxides and fragments of diatoms. The sediment is predominantly very fine-grained and video from both the Nereus traverses across the Challenger Deep in 2009 and from the Deepsea Challenger submersible dive by James Cameron in 2012 indicate recent resurfacing of the trench axis. This is consistent with the high degree of deformation and frequency of earthquakes in the southern Mariana forearc north of the trench. An apron of self-derived talus blankets the lower part of the inner trench slope and fines from submarine landslides are the likely source of the trench axis sediment. Rock samples collected using Nereus from deep (10,879 m) on the incoming plate south of the Challenger Deep are partially altered microgabbros with interstitial glass containing microtubules similar to those observed in a variety of marine settings in lavas and hypabyssal igneous rocks. The tubules are presumed to be caused by tunneling of lithoautotrophic microbes into the glass. The rocks were collected from a site at the base of a fault scarp where large columnar-jointed blocks are draped with sediment. The igneous basement of the subducting plate south of the Challenger Deep is, as yet, undated, but it may be younger than the Jurassic Pacific Plate subducting beneath the southeastern Mariana forearc. There is the suggestion of a boundary between and the Pacific Plate and the shallower sea floor (Caroline plate?) subducing beneath the southernmost arm of the Mariana Trench. Early interpretations by Hegarty and Weissel (1988) and more recently by Lee (2004) are that the chain of seamounts striking NNW, colinear with the Lyra Trough, might mark such a boundary. Age dating of the microgabbro recovered with Nereus should help to solve this question.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2013
- Bibcode:
- 2013AGUFM.T54B..07F
- Keywords:
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- 1031 GEOCHEMISTRY Subduction zone processes;
- 3070 MARINE GEOLOGY AND GEOPHYSICS Submarine landslides;
- 3075 MARINE GEOLOGY AND GEOPHYSICS Submarine tectonics and volcanism;
- 3080 MARINE GEOLOGY AND GEOPHYSICS Submergence instruments: ROV;
- AUV;
- submersibles