共查询到20条相似文献，搜索用时 15 毫秒
1.
2.
3.
4.
Petrogenetic mixing models and Nd-Sr isotopic patterns 总被引：1，自引：0，他引：1
5.
6.
7.
Michael L. Bender 《Geochimica et cosmochimica acta》1973,37(5):1229-1247
8.
W.A. Russell D.A. Papanastassiou T.A. Tombrello 《Geochimica et cosmochimica acta》1978,42(8):1075-1090
9.
10.
11.
12.
13.
14.
15.
16.
D.J Whitford 《Geochimica et cosmochimica acta》1975,39(9):1287-1302
Pleistocene and Recent lavas from the Sunda arc range from those showing affinities with the island arc tholeiitic series, through a spectrum of calc-alkaline to high-K alkaline rocks. The tholeiitic rocks have relatively low ratios averaging 0–7043; the calc-alkaline rocks show a wide range (from 0.7038 to 0.7059, averaging 0.7048); the high-K alkaline rocks average 0.7045. A rhyolitic ignimbrite from Sumatra has an ratio of 0.7139.The relationship between and major and trace element geochemistry is variable and complex. Lavas from the same volcano sometimes show significant differences in despite close geochemical relationships. Rocks of the calc-alkaline suite show a regular decrease in from West Java to Bali and there is some evidence for increasing with increasing depth to the Benioff zone. Calc-alkaline and tholeiitic rocks from the Sunda arc have significantly higher ratios than those from other island arcs, except from those arcs where continental crustal involvement has been inferred (e.g. New Zealand).A model of 87Sr enrichment due to isotopic equilibration of oceanic crust with sea water and disequilibrium melting in the slab and/or mantle is favoured to explain the Sr isotopic composition of the tholeiitic and normal calc-alkaline lavas. Calc-alkaline lavas with high ratios are best explained by either sialic contamination, or the presence of alkali basalt as a component of the downgoing slab. The Sr isotopic data for the high-K alkaline lavas suggest a mantle origin. The high ratio in the Lake Toba rhyolite implies a crustal origin. 相似文献
17.
18.
19.
Norbert Clauer Michel Hoffert Anne-Marie Karpoff 《Geochimica et cosmochimica acta》1982,46(12):2659-2664
Morphological, mineralogical, chemical and RbSr isotopic studies have been made on Fesmectites (nontronites) from southern Pacific red clays cored near the Marquisas Islands. These minerals have at the top of the core, an ratio of 0.70917 ± 0.00007, which indicates an authigenic origin in isotopic equilibrium with seawater. Weak leaching experiments with 1N HCl show that the nontronites also contain a volcanic component with a lower ratio which, combined with the morphology of the particles, suggests a transportation by bottom currents of clay formed elsewhere.During burial, the nontronites experience diagenetic modifications resulting in an increase in Fe, K and Rb contents, a concomitant decrease of Mg, Ca, Ti, Na and Sr, and a preferential migration of radiogenic 87Sr from the clays into the surrounding pore waters.The ratio of the Sr adsorbed on the outermost surfaces of the nontronites does not change with depth in the core, and is, therefore, independent of diagenetic influence, which is rather characterized by the ratios of the interstitial waters. The isotopic composition of both the adsorbed Sr and that of the pore fluids may yield useful information on the crystallization environment and subsequent history of deep sea red clays. 相似文献