Incompatible element

About: Incompatible element is a research topic. Over the lifetime, 2420 publications have been published within this topic receiving 154052 citations.

Magnetic Properties and Incompatible Element Geochemistry of Some Igneous Rocks from Deep Sea Drilling Project Leg 64

Abstract: The experimental method is described by Verma and Banerjee (in press). All magnetic measurements were taken at the rock magnetism laboratory, University of Minnesota. Tables 1 and 2 present these results. Natural remanent magnetization (NRM) intensity (Jn) varies from 0.374 to 10.6 × 10~ 3 emu cm-. Corresponding anhysteritic remanent magnetization (ARM) intensity (Ja) ranges from 0.498 to 11.0 × 10 ~ 3 emu cm-. Thus, /„ and Ja show somewhat similar ranges of variation. Dolerites from Site 478 possessing lower Jn values are more altered than the other samples. Viscous remanent magnetization (VRM) acquisition experiments conducted for about 30,000 min. show rather small but measurable VRM components. The VRM growth curves consist of two or three distinct segments of generally increasing slopes. Such growth curves have been obtained by other investigators in other sites (Lowrie, 1974; Kent and Lowrie, 1977; Verma and Banerjee, in press). Least-square fitting of the data permits their extrapolation for I0 min. (Jvex). The results show that these younger dolerites are considerably less viscous than the diabases (dolerites) from Leg 63 (Verma and Banerjee, in press). The gabbro from Hole 481A shows a VRM acquisition similar to the dolerites in the present study. I tested the stabilities of the three magnetizations (NRM, ARM, and VRM) by stepwise alternating field (AF) demagnetization. Figure 1 shows the demagnetization curves. The ARM and NRM show similar demagnetization curves, especially for the latter three samples. But the VRM consistently shows much lower stability. Thus, a large part of the NRM in these rocks may be the original thermal remanent magnetization (TRM) component, and VRM may not T?e a serious problem for these samples. The weak-field susceptibility (x) of these samples ranges from 11 to 31 × 10~ emu (cmOe-) The

Chemical compositions and Sr, Nd isotope ratios of gabbroic xenoliths in calc-alkali andesites of Naeba and Torikabuto volcanoes, North Fossa Magna, central Japan

Abstract: Gabbroic, doleritic and basaltic xenoliths found in calc-alkali andesites of Naeba and Torikabuto volcanoes are geochemically divided into three groups. Gabbro A of the group 1 from Naeba is rich in MgO and Ni, poor in alkalis, and shows depleted REE pattern resembling those of Ichinomegata (Sp. No. 2232) and Hakone (HKG1, HKG2) volcanoes. On the basis the REE pattern and high Al ?? V contents in clinopyroxenes, gabbro A is interpreted to have been cumulate from a primary magma generated by partial melting of upper mantle. From REE pattern, gabbros of the group 2 from Ichinomegata (Sp. No. 2218) may have derived from low alkali tholeiite magma which have been formed by removal of material such as the group 1 gabbro at shallow depth. Doleritic and basaltic xenoliths of the group 3 from Naeba, gabbroic xenoliths from Torikabuto and Umikawa are poorer in MgO and richer in alkalis than those of the group 1 and show enriched pattern in REE resembling that of high alkali tholeiite and contain clinopyroxenes having low Al ?? V. Therefore, these rocks are considered to be differentiates of high alkali tholeiite magma at shallow depth. On eNd-87Sr/8 ?? Sr diagram, isotope data of gabbro A of the group 1 plot near those of andesites from Asama and Myoko volcanoes of the North Fossa Magna. It is interpreted that these rocks have derived from the same mantle source as the Asama and Myoko volcanoes which are richer in incompatible elements than those of MORB.

Trace elements and Sr-Nd isotopic geochemistry and genesis of Jijie alkaline-ultramafic rocks,southern part of Panxi rift

Abstract: The Jijie alkaline complex is located in the southern part of Panxi rift,Yunnan Province.Jijie alkaline-ultramafic rocks complex body mainly is composed of melteigites,ijolites and urtites.They all have similar primitive mantle-normalized trace element spider diagram and REE(Rare Earth Element) patterns.The complex show relative enrichment of large-ion lithophile,such as K,Rb,Sr,Ba and relatively low contents of Sc,Cr and Ni.The Nb/Ta and Zr/Hf ratios are spread within the range of mantle-droved rocks.Sr and Nd isotope distribute along the"mantle array".Whereas,the contents of all the incompatible elements are relatively lower than OIB(Ocean Island Basalts) and other alkaline rocks,and comparable with E-MORB(Enriched-Mid Ocean Ridge Basalts).The low contents of ΣREE = 32.86 ～ 70.07,(La/Yb) N = 3.03 ～ 4.47 and strongly negative HREE,suggest that the peridotite mantle source have garnet residual and depleted incompatible elements.The primitive magma of Jijie alkaline-ultramafic rocks was underwent low-degree( 10%) partial melt at high pressure,mainly experienced olivine,clinopyroxene and a slight magnetite crystal fractionation during the magma evolution.Melteigite,ijolite and urtite were derived from the same mantle source.The depleted mantle source of Jijie alkaline-ultramafic rocks may be related to the large volumes of Emeishan basalt magmas droved from mantle during Middle-Late Permian in this area.As the multi-stage activities of Paxnxi rift has provide a channel for Emeishan mantle plume,the alkaline magma originated from the lithosphere mantle or mixed mantle low degree partial melting during the early or late stages of Emeishan mantle plume activity invaded along Panxi rift.

Geochemical evidence for low magma supply and inactive propagation at the Galápagos 93.25°W overlapping spreading center

Abstract: [1] Major and trace element concentrations; Sr, Nd, and Pb isotopic ratios; and plagioclase and olivine compositions of samples from 92°35′W to 94°10′W on the Galapagos Spreading Center (GSC) constrain magmatic processes associated with the 93.25°W overlapping spreading center (OSC). Significant variations in parental magma compositions and extent of low-pressure fractionation over short along-axis distances suggest small, discontinuous, or poorly mixed magma chambers. Mineralogical, petrological, and geochemical data indicate this OSC is characterized by low overall melt supply. Regional along-axis geochemical gradients along the western GSC (e.g., in 206Pb/204Pb, Nb/Zr, and La(8)/Sm(8)) are interrupted by increased variability within the OSC, consistent with less efficient mixing of melts in this region. Despite a long-term history of westward propagation, bathymetric and geochemical data are inconsistent with recent propagation of this offset; the eastern limb appears to have recently retreated and left behind a series of abandoned ridges within the overlap zone. The eastern limb shows two progressive westward trends of decreasing ratios of highly to moderately incompatible elements, one outside and one within the overlap zone. The overlapping portion of the western limb also has low ratios of these elements. These patterns are consistent with previously depleted mantle being preferentially melted beneath this offset.