Dependence of mid-ocean ridge morphology on spreading rate in numerical 3-D models

2014 ◽  
Vol 25 (1) ◽  
pp. 270-283 ◽  
Author(s):  
C. Püthe ◽  
T. Gerya
Keyword(s):  
Spreading Rate ◽  
Mid Ocean Ridge ◽  
Ocean Ridge

scholarly journals Lithogeochemistry of the Mid-Ocean Ridge Basalts near the Fossil Ridge of the Southwest Sub-Basin, South China Sea

Minerals ◽  
2020 ◽  
Vol 10 (5) ◽  
pp. 465 ◽  
Author(s):  
Kai Sun ◽  
Tao Wu ◽  
Xuesong Liu ◽  
Xue-Gang Chen ◽  
Chun-Feng Li
Keyword(s):  
South China Sea ◽  
Partial Melting ◽  
Fractional Crystallization ◽  
South China ◽  
Spreading Rate ◽  
Tholeiitic Basalt ◽  
Spinel Peridotite ◽  
China Sea ◽  
Mid Ocean Ridge ◽  
Ocean Ridge

Mid-ocean ridge basalts (MORB) in the South China Sea (SCS) record deep crust-mantle processes during seafloor spreading. We conducted a petrological and geochemical study on the MORBs obtained from the southwest sub-basin of the SCS at site U1433 and U1434 of the International Ocean Discovery Program (IODP) Expedition 349. Results show that MORBs at IODP site U1433 and U1434 are unaffected by seawater alteration, and all U1433 and the bulk of U1434 rocks belong to the sub-alkaline low-potassium tholeiitic basalt series. Samples collected from site U1433 and U1434 are enriched mid-ocean ridge basalts (E-MORBs), and the U1434 basalts are more enriched in incompatible elements than the U1433 samples. The SCS MORBs have mainly undergone the fractional crystallization of olivine, accompanied by the relatively weak fractional crystallization of plagioclase and clinopyroxene during magma evolution. The magma of both sites might be mainly produced by the high-degree partial melting of spinel peridotite at low pressures. The degree of partial melting at site U1434 was lower than at U1433, ascribed to the relatively lower spreading rate. The magmatic source of the southwest sub-basin basalts may be contaminated by lower continental crust and contributed by recycled oceanic crust component during the opening of the SCS.

scholarly journals Assessing the impact of sedimentation on fault spacing at the Andaman Sea spreading center

Geology ◽  
2020 ◽  
Author(s):  
Clément de Sagazan ◽  
Jean-Arthur Olive
Keyword(s):  
Active Faults ◽  
Spreading Rate ◽  
Andaman Sea ◽  
Spreading Center ◽  
Normal Faults ◽  
Mid Ocean Ridge ◽  
Plate Separation ◽  
Slow Spreading ◽  
Ocean Ridge ◽  
The Impact

The stabilizing effect of surface processes on strain localization, albeit predicted by several decades of geodynamic modeling, remains difficult to document in real tectonic settings. Here we assess whether intense sedimentation can explain the longevity of the normal faults bounding the Andaman Sea spreading center (ASSC). The structure of the ASSC is analogous to a slow-spreading mid-ocean ridge (MOR), with symmetric, evenly spaced axis-facing faults. The average spacing of faults with throws ≥100 m (8.8 km) is however large compared to unsedimented MORs of commensurate spreading rate, suggesting that sedimentation helps focus tectonic strain onto a smaller number of longer-lived faults. We test this idea by simulating a MOR with a specified fraction of magmatic plate separation (M), subjected to a sedimentation rate (s) ranging from 0 to 1 mm/yr. We find that for a given M ≥ 0.7, increasing s increases fault lifespan by ~50%, and the effect plateaus for s > 0.5 mm/yr. Sedimentation prolongs slip on active faults by leveling seafloor relief and raising the threshold for breaking new faults. The effect is more pronounced for faults with a slower throw rate, which is favored by a greater M. These results suggest that sedimentation-enhanced fault lifespan is a viable explanation for the large spacing of ASSC faults if magmatic input is sufficiently robust. By contrast, longer-lived faults that form under low M are not strongly influenced by sedimentation.

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