International Ocean Discovery Program; Expeditions 367 and 368 scientific prospectus; South China Sea rifted margin; testing hypotheses for lithosphere thinning during continental breakup; drilling at the South China Sea rifted margin

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doi: 10.14379/iodp.sp.367368.2016
Author(s): Sun Zhen; Jian Zhimin; Stock, Joann; McIntosh, Kirk; Klaus, Adam; Alvarez-Zarikian, Carlos A.
Author Affiliation(s): Primary:
South China Sea Institute of Oceanology, Laboratory of Marginal Sea and Ocean Geology, Guangzhou, China
Tongji University, China
California Institute of Technology, United States
University of Texas-Austin, United States
Texas A&M University, United States
Source: Scientific Prospectus (International Ocean Discovery Program), Vol.367/368, 57p. Publisher: International Ocean Discovery Program, College Station, TX, United States. ISSN: 2332-1385
Note: In English. 52 refs.
Summary: International Ocean Discovery Program (IODP) Expeditions 367 and 368 will address the mechanisms of lithosphere extension during continental breakup. State of the art deep reflection seismic data show that the northern South China Sea (SCS) margin offers excellent drilling opportunities that can address the process of plate rupture at a magma-poor rifted margin. The SCS margin shows similarities to the hyperextended Iberia-Newfoundland margins, possibly including exhumed and serpentinized mantle within the continent-ocean transition (COT). However, recent modeling studies suggest that mechanisms of plate weakening other than serpentinization of the subcontinental lithospheric mantle exist. Two competing models for plate rupture (in the absence of excessively hot asthenospheric mantle) have widely different predictions for (1) the crustal structure across the COT, (2) the time lag between breakup and formation of igneous ocean crust, (3) the rates of extension, and (4) the subsidence and thermal history. Proposed drilling will core through thick sedimentary sections and into the underlying basement to firmly discriminate between these models. We plan to occupy four sites across a 150-200 km wide zone of highly extended seaward-thinning crust with a well-imaged COT zone. Three sites will determine the nature of critical crustal entities within the COT and constrain postbreakup crustal subsidence. These three sites will also help constrain how soon after breakup igneous crust started to form. A fourth site on the continental margin landward of the COT will constrain the timing of rifting, rate of extension, and crustal subsidence. If serpentinized mantle is found within the COT, this will lend support to the notion that the Iberia type margin is not unique, and hence that weakening of the lithosphere by introducing water into the mantle may be a common process during continental breakup. If serpentinite is not found, and alternatively, scientific drilling results for the first time are gained in support of an alternative model, this would be an equally important accomplishment. Constraints on SCS formation and stratigraphy, including industry drilling, Ocean Drilling Program Leg 184 and IODP Expedition 349 drilling, the young (Paleogene) rifting of the margin, and absence of excessively thick postrift sediment allow us to effectively address these key topics by drilling within a well-constrained setting. An initial spreading rate of ∼2 cm/y half-rate reduces the potential complexity of magma-starved, slow-spreading crust forming after breakup. Drilling, coring, and logging to address these SCS rifted margin science objectives will be undertaken during Expeditions 367 and 368, which will be implemented as a single science program.
Year of Publication: 2016
Research Program: IODP Integrated Ocean Drilling Program
IODP2 International Ocean Discovery Program
ODP Ocean Drilling Program
Key Words: 18 Geophysics, Solid-Earth; 20 Geophysics, Applied; Boreholes; Cenozoic; Continental margin; Crust; Crustal thinning; Drilling; Expedition 349; Expedition 367; Expedition 368; Extension tectonics; Geophysical methods; Geophysical profiles; Geophysical surveys; Integrated Ocean Drilling Program; International Ocean Discovery Program; Leg 184; Lithosphere; Magnetic anomalies; Mantle; Marine drilling; North Pacific; Northern South China Sea; Northwest Pacific; Ocean Drilling Program; Oceanic crust; Pacific Ocean; Planning; Plate tectonics; Programs; Rifting; Sea-floor spreading; Seismic methods; Seismic profiles; South China Sea; Surveys; Tectonics; West Pacific
Coordinates: N100000 N220000 E1200000 E1100000
Record ID: 2016047578
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