Meeting

Neotectonics in the Southwest Sub-basin, South China Sea: Constraints from multi-channel seismic data and IODP Expedition 349

The neotectono-sedimentary processes of the South China Sea abyssal basin have long been a puzzling issue and are still debated because of the lack of drilling evidence. In this study, we interpreted four multi-channel seismic profiles across the Southwest Sub-basin (SWSB), integrated for stratigraphic correlation with new drilling data from the Integrated Ocean Discovery Program (IODP) 349 Expedition. Results show that the Neogene sediments are divided into four stratigraphic units, each with distinctive seismic reflectors.

Investigation of turbulent flows and near-bottom hydrothermal plumes at mid-ocean ridges

We investigate the characteristics of turbulent flows within near-bottom hydrothermal plumes at mid-ocean ridges through quantitative analysis of video images from manned submersibles using the Particle Image Velocimetry (PIV) method. High-quality video images of near-bottom hydrothermal vents were selected from the Data Library and Archives of the Woods Hole Oceanographic Institution (WHOI), consisting of multiple examples of vent fields in the Atlantic, Pacific, and Indian Oceans.

Interpretation of the spreading process for the narrow low-latitude inactive ocean basin using deeptow magnetic anomalies: A case study of Southwest Subbasin, South China Sea

Marine magnetic lineation is an important media to interpret the age and spreading process of the oceanic crust. But there are many difficulties to identify the lineation from sea surface observation in a deep and narrow inactive ocean basin located in the low-latitude. Located in such a tectonic position, the spreading history of the Southwest subbasin of the South China Sea became a long time controversy. the deeptow data were able to increase observed anomaly amplitudes by a factor of ~4.

Different Crust Failure Modes Controlled by Spreading Obliquity and Its Implication: Insight from Southwest Indian Ridge 46-52.5°E

Oblique spreading occurs when the direction of relative motion between two rigid plates is oblique to the mid-ocean ridge trend. The main oblique spreading ridges are the Southwest Indian Ridge (Dick et al., 2003), Sheba Ridge (Lepvrier et al., 2002), Reykjanes Ridge (Dauteuil and Brun, 1993), Mohns Ridge (Wijk and Blackman, 2007), and Knipovich Ridge (Okino et al., 2002).

Crustal evolution from the Costa Rica Rift to borehole 504B

Oceanic crust undergoes rapid transformation in both its thermal and physical structure within the first 10 Ma from the ridge axis. Large departures in observed heat flow measurements from global depth and heat flow models reveal the importance of hydrothermal systems in heat dissipation and crustal alteration. Hydrothermal systems have the greatest influence on young oceanic crust due to its high porosity and permeability and low sediment cover. Much is still unknown about the scale and processes involved, especially the interaction between the solid Earth and the oceans.

Asymmetric crustal structure of the slow-spreading Mohns Ridge

We investigate the relationship among hotspot influence, local magma supply, and asymmetric topography and crustal structure of the conjugate flanks of the slow-spreading Mohns Ridge. Residual mantle Bouguer anomaly (RMBA) was calculated by subtracting from free-air gravity the predicted attractions of water-sediment, sediment-crust, and crust-mantle interfaces as well as the effects of lithospheric cooling.

Geophysical analysis of oceanic crust at a mid-ocean ridge

The NERC-funded joint geophysical and oceanographic OSCAR project aims to develop understanding of the interactions between relatively young oceanic crust and the overlying abyssal ocean through heat transfer and fluid flow. The movement of hydrothermal fluids through the oceanic crust causes changes in its structure and composition: circulating heat, precipitating minerals in open cracks and fractures, and forming alteration fronts which influence permeability and seismic properties, though little is known about the rate and extent of these processes. 

InterRidge Bursary to Panama Basin and preliminary bathymetric interpretation

The InterRidge cruise bursary is aimed at post graduate students seeking cruise experience. This provides a vital opportunity for training in data collection and experience of scientific principles in action.  The bursary allowed me to join Dr. R. Hobbs’ JC114 cruise to the Panama basin to study the Costa Rica and Ecuador ridges. Subsequently after the cruise I became involved in the OSCAR project, ‘Oceanographic and Seismic Characterisation of heat dissipation and alteration by hydrothermal fluids at an Axial Ridge’.

Review of Os isotope variation and model ages in ablyssal peridotite

Abyssal peridotites are of great interest to geoscientists because they provide direct information about the present-day Earth's mantle. Os isotope systems in abyssal peridotites are also interesting because Os is a highly siderophile and compatible element and so concentrates in the core in preference to the mantle, and in the mantle in preference to the crustal materials. In addition, Os in abyssal peridotites is not susceptible to metasomatism and alteration by sea water.

Systematic variations in morphological characteristics of global transform faults

We quantify systematic variations in morphological characteristics of global transform faults and investigate their dependence on spreading rate, local magma supply, and other tectonic variables. Detailed analyses were conducted on 78 transform faults where high-resolution multibeam bathymetry and other geophysical data are available.

Tamu Massif-Largest Volcano on Earth-within Shatsky Rise Oceanic Plateau Formed by Mantle Plume-Mid-Ocean Ridge Interaction?

Jinchang Zhang1,2, William W. Sager2,3, Jun Korenaga4

 

1South China Sea Institute of Oceanology, Chinese Academy of Sciences, China

2Texas A&M University, College Station, Texas, USA

3University of Houston, Houston, Texas, USA

A New Method of Automatic SVP Optimization Based on MOV Algorithm

We applied the maximum offset of sound velocity algorithm to sound velocity profile streamlining and optimization to overcome multi-beam survey and data processing efficiency problems. The impact of sound velocity profile streamlining on sounding data accuracy is evaluated. By automatically optimizing the threshold, the reduction rate of sound velocity profile data can reach over 90% and the standard deviation percentage error of sounding data can be controlled to within 0.1%.

Rare-earth-elements characteristics of the hydrothermal sulfide in the Central Indian Ridge

 A new method is proposed to identify automatically the foot of the continental slope (FOS) based on the integrated analysis of topographical profiles. First, it simplifies the topographic profiles based on second derivative extremum points and the Douglas-Peucker algorithm, and calculates a second-order derivative of the original profiles and the D-P profiles. Then, seven steps are used to simplify the original profiles and determine the slope gradient, water depth and second derivative values of data points.

Geochemical features of the hydrothermal sulfide on the Southern Mid-Atlantic Ridge near 15°S

With a systematic study on mineralogy of the three stations’ sulfide samples dredged from the seafloor hydrothermal field near 15°S Southern Mid-Atlantic Ridge, geochemical features of these sulfides are also described in detail. Bulk chemical analyses of sulfide samples were obtained using X-ray Fluorescence (XRF) and Inductively Coupled Plasma Mass Spectrometry (ICP-MS). The sulfides on the Southern Mid-Atlantic Ridge (SMAR) near 15°S can be divided into three types: Fe-rich sulfide, Fe-Cu-rich sulfide and Fe-Zn-rich sulfide, and enrich Fe, Zn and Cu concentrations successively.

TPEC Algorithm and its Application in Niao Chao Hill —China’s first international undersea feature naming

In recent years, Sub-Committee on Undersea Feature Names (SCUFN) has been conducting deliberations on naming undersea features that are entirely or mainly (more than 50%) outside the external limits of the territorial sea, adhering to the principles of not involving sovereignty dispute between countries. In order to participate in undersea feature naming and embody the international responsibility, obligation and influence of the State, Chinese State Oceanic Administration submitted seven undersea name proposals to SCUFN in 2011 for the first time.