Geo-chemical Characteristics of the Sediments in Southwest Indian Ridge
Abstract
Major elements,trace elements and rare earth elements measurements were carried out on twenty-one sediment samples taken from the Leg II and III in Chinese reasearch cruise DY-30 which explored in Southwest Indian Ridge. The results show that all of the samples can be divided into to two groups: Si-rich group and Ca-rich group. Similar to silicates/aluminosilicates, Si-rich group sediments enrich Si(SiO2:34% to 49.6%), Mg(MgO:4.92% to 27.5%),Fe (Fe2O3:7.78% to 10.65%)and Al(Al2O3:4.87% to 12.15%) , which are very different from Ca-rich group sediments that enrich Ca(CaO:39.7%~53.9%), LOI(29.32% to 42.98%) and Sr(972ppm to 1680ppm) that are similar to biogenetic carbonate. The variation range of ∑REE of Si-rich group sediments is 12.89ppm to 44.90ppm similar to Ca-rich group sediments that is 16.82ppm to 35.11ppm, while the ratio of LREE/HREE of Si-rich group sediments(1.03 to 1.83) is much less than Ca-rich group sediments(2.39 to 5.36). The normalized REEs with North American Shale Composite(NASC) in samples show N-MORB characteristics in Si-group sediments though the ∑REE are a bit lower, and slight negative Ce anomaly in both two groups(δCe: 0.80 to 0.43) while positive Eu anomaly is relatively distinctive in Si-group sediments(δEu: 1.14 to 1.60). Contens of CaO+LOI in Ca-rich group sediments are mostly higher than 80%(even 90%) indicate biodeposition is prominent in contrast to Si-rich group sediments(CaO+LOI: 11.33% to 46.68% ) that are concerned with the mixture of basalt, ultrabasic rocks and calcareous sediments. The good correlation coefficients for major elements (SiO2,Al2O3,MgO,TiO2 and LOI) corrected by CaO(for mitigating the effects of biodeposition) in Si-rich sediments with the comparison of the ∑REE-P2O5 among the Si-rich group sediment, Ca-rich group sediments and basalt in Southwest Indian Ridge also support the basalt is the main material source of Si-rich group sediment. Both of the δCe values and the U/Th-V/(V+Ni)plot show an oxide sedimentary environment, and content of CaO with linearity among the major elements in Ca-rich group sediments point out the study area is above the Carbonate compensation depth(CCD) and sedimentary environment is quite stable.
- Publication:
-
EGU General Assembly Conference Abstracts
- Pub Date:
- April 2015
- Bibcode:
- 2015EGUGA..1714754H