Significance of fractures and veins in the basalt at site U1431 and U1433, International Ocean Discovery Program Expedition 349, South China Sea

Author(s): Sun, Zhen; Ding, W.
Author Affiliation(s): Primary:
Chinese Academy of Sciences, South China Sea Institute of Oceanology, Guangzhou, China
Other:
State Oceanographic Administration of China, China
Volume Title: AGU 2014 fall meeting
Source: American Geophysical Union Fall Meeting, Vol.2014; American Geophysical Union 2014 fall meeting, San Francisco, CA, Dec. 15-19, 2014. Publisher: American Geophysical Union, Washington, DC, United States
Note: In English
Summary: During International Ocean Discovery Program (IODP) Expedition 349, we successfully cored basalts along the central relict spreading ridge, in both the East Subbasin at Site U1431 and the Southwest Subbasin at Sites U1433 and U1434. Due to low recovery (<20%), Site U1434 provides little opportunity to analyze fractures and veins; however, we carefully described and analyzed fractures and veins at Sites U1431 and U1433. Several hundred fractures and veins were observed and we measured ∼75% of those, whereas the other ∼25% are either irregular or in small branches and thus could not be measured easily. Most of the fractures and veins have no obvious lateral offset or striations on the fractured surface. The veins are generally infilled fractures, whereas many fractures are reactivated along preexisting veins. Thus, the total number of fractures and veins can be used as an indicator of the degree of rock fragmentation. Shapes and contact relationships suggest that most of the fractures and veins resulted from cooling effects. Comparison between fracture and vein frequency with lithology indicates that high fragmentation occurs in the pillow basalt, whereas low fragmentation corresponds to massive flow basalt at Site U1433. At Site U1431, the relationship is similar, but more complicated. The frequency of fractures and veins at Site U1431 is almost double that of Site U1433. The basalt is also more altered at Site U1431 than U1433. These results provide constraints on investigation of the rock fragmentation and alteration processes of basaltic basement of the South China Sea.
Year of Publication: 2014
Research Program: IODP Integrated Ocean Drilling Program
IODP2 International Ocean Discovery Program
Key Words: 07 Marine Geology and Oceanography; Cores; Expedition 349; IODP Site U1431; IODP Site U1433; International Ocean Discovery Program; Marine sediments; North Pacific; Northwest Pacific; Pacific Ocean; Sediments; South China Sea; West Pacific
Coordinates: N125508 N125508 E1150251 E1150250
N152232 N152233 E1170001 E1165959
Record ID: 2015073681
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