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doi:10.14379/iodp.sp.367368.2016

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 margin1


Zhen Sun

Expedition 367 Co-Chief Scientist

Key Laboratory of Marginal Sea and Ocean Geology

South China Sea Institute of Oceanology

164 Xingangxi Road

Haizhu District, Guangzhou

China

zhensun@scsio.ac.cn

Joann Stock

Expedition 367 Co-Chief Scientist

Division of Geological and Planetary Sciences

California Institute of Technology

1200 East California Boulevard

Pasadena CA 91125

USA

jstock@gps.caltech.edu

Adam Klaus

Expedition 367 Expedition Project
Manager/Staff Scientist

International Ocean Discovery Program

Texas A&M University

1000 Discovery Drive

College Station TX 77845

USA

aklaus@iodp.tamu.edu

Zhimin Jian

Expedition 368 Co-Chief Scientist

State Key Laboratory of Marine Geology

Tongji University

Siping Road 1239

Shanghai 200092

China

jian@tongji.edu.cn

Kirk McIntosh

Expedition 368 Co-Chief Scientist

University of Texas Institute for Geophysics

10100 Burnet Road (R2200)

Building 196

Austin TX 78758-4445

USA

kirk@ig.utexas.edu

Carlos A. Alvarez-Zarikian

Expedition 368 Expedition Project
Manager/Staff Scientist

International Ocean Discovery Program

Texas A&M University

1000 Discovery Drive

College Station TX 77845

USA

zarikian@iodp.tamu.edu

Published April 2016

See the full publication in PDF.

Abstract

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.


1Sun, Z., Stock, J., Jian, Z., McIntosh, K., Alvarez-Zarikian, C.A., and Klaus, A., 2016. Expedition 367/368 Scientific Prospectus: South China Sea Rifted Margin. International Ocean Discovery Program. http://dx.doi.org/‚Äč10.14379/‚Äčiodp.sp.367368.2016