Incompatible element

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

The Heterogeneous Icelandic Plume: Constraints from Pb Isotopes and Trace Element Ratios

Abstract: Although the volcanic rocks of Iceland have been the subject of numerous geochemical investigations, none has included both Pb isotopes and precisely determined trace-element ratios. This combination, when used together with existing petrological and geochemical data, has the potential to provide strong constraints on the composition and origin of the Iceland plume, the manner in which it interacted with surrounding mantle, and the way in which it melted. We report here measurements on well documented (H6mond et al. 1988, 1993) mafic volcanic rocks from all parts of the island. Compositions range from picrite to alkali basalt and include the most common olivine and quartz tholeiites. Extended trace-element patterns show a wide range, from strong depletion of incompatible elements ((La/Sm)y=0.5) in the picrites, to moderate enrichment ((La/Sm)N=2.7) in 206 204 the alkali basalts. Pb/ Pb ratios vary from 18.0 in picrites to 19.2 in alkali basalts. These ratios correlate with both 2~176 and 2~176 and with Ce/Pb which is as low as 10.7 in picrites and as high as 46.8 in alkali basalts. In addition, Ce/ Pb correlates both with Sm/Hf and with the size of positive Sr and Ba anomalies which are large and conspicuous in the picrites. In contrast with the strong correlation beween chemical composition and rock type, there is no systematic relationship between isotopic or trace-element ratios and the geographic position of the samples. Correlations are also observed between Ce/Pb, Sr/Nd, Sm/Hf and 8~So which ranges from +3%o in the alkali basalts to +6%0 in the picrites. Even though some of the trace-element characteristics can be attributed to extreme fractionation during melting (Elliott et al., 1991), most of the variations that we report here cannot. The mantle-like 61SO of the picrites argue against an hydrothermal origin for the positive Sr and Ba anomalies and rules out an important role for interaction of magmas with the present Icelandic crust. Correlations between isotopic compositions and ratios such as Sr/Nd, Sin/ G6osciences Rennes, UPR 4661-CNRS, Universit6 de Rennes 1, 35042 Rennes Cedex, France

The mantle characteristics of quaternary continental lithosphere,southeast coast of china

Abstract: The peridotite xenoliths in the Cenozoic basalts came from young lithospheric mantle in the southeastern China. These peridotites contain a great deal of information of deep processes. There are a great number of differences in petrology, mineralogy, trace elements and Sr-Nd isotopic compositions in the peridotite xenoliths. These differences show that these peridotite xenoliths have undergone different mantle processes. The South China Sea spreading is regarded to relate to the mantle plume. The peridotite xenoliths in the Quaternary volcanic rocks after the South China Sea spreading may reserve more information about the mantle plume. The mineral compositions of peridotite xenoliths are similar to the abyssal peridotites. The xenoliths are depleted in Opx and enriched in Ol, and enriched in strongly incompatible elements, which patterns are similar to those of their host rocks. In addition, the xenoliths are more depleted than MORB in Sr-Nd isotopic compositions. The continental lithosphere was subjected to further alteration by the SiO 2-poor melts from the deep mantle.

Molybdenittmineraliseringer i Kleivangranitten, Lyngdal

Abstract: Mineralization of molybdenite were discovered in the Kleivan granite, Lyngdal and document that the ore-forming potential of this rare example of a differentiated, A-type, granite. The cryptic zonation up through the igneous stratigraphy was confirmed and is the result of fractional crystallization. A decrease in compatible elements (Sc, Zr, Ba, Ti, Sr, Fe, Zn and Cu) and an increase in incompatible elements (mostly Rb) towards the most evolved parts of the intrusion are advantageous for the genesis of an H2O phase enriched in Mo. Field observations of molybdenite in aplite and pegmatite in the cupola of the Kleivan granite, together with veins and veinlets of quartz imply that magmatic-hydrothermal ore forming processes were active. A high abundance of primary fluid inclusions in magmatic quartz in the upper part of the intrusion show that igneous aqueous fluids in deed were present during solidification of this part of the intrusion. However, regular hydrothermal stockwork mineralizations are not exposed. They may be present somewhere in the roof section of the hostrock that is covered by quarternary sediments or, simply they never formed. Mineralization of molybdenite in aplites and pegmatite`s formed during terminal of the Kleivan intrusion supports that the conditions for molybdenite formation were present (fO2, S and decreasing T). Calculations of the size of a possible Mo deposit with different initial Mo (1, 15, 29 ppm) in the parent melt at different thicknesses (1.5, 3, 6, 12 km) of the intrusion gives reasonable sizes of a deposit. Mo will apparently not be a limiting factor in the ore forming process. The amount of exsolved H2O in the Kleivan granite is unknown and is crucial in the control of the ore forming process. The discovery of spinel ([Zn, Fe]Al2O4) and chrysoberyll (BeAl2O4) in the apex of the intrusion, together with the occurrence of sillimanite and garnet makes a complex petrography and the Al rich conditions here.The contents of Mo in rocks from the early crystallization of the intrusion are surprisingly low (<1 ppm). In aplite and pegmatite in the upper part of the intrusion, the content of Mo is considerably higher (from 10 to 600 ppm). The theory of a hydrothermal fluid scavenging the melt for Mo is supported by these findings. Finding a magmatic hydrothermal mineralization of molybdenite associated with the Kleivangranite is highly possible. The potential for further exploration in the Kleivan granite in the search for an interesting molybdenite deposit is present.

Study on the Geological and Geochemical Characteristics of Quartz Porphyry in Song County,Henan Province

Abstract: Song county,situated in the Xiong'er Shan Mountains,western Henan province,is rich in gold deposits.In geology this area is of Neoarchean Taihua Group and Mesoproterozoic Xiong'er Group strata,with high-grade metamorphism,intense tectonic movements,and frequent magmatic activities.During the Yanshan period,much intermediate-acid intrusive magma produced associated typical small ore-bearing porphyries,such as quartz porphyry.Based on the field geological observations and indoor chemical analysis on quartz porphyry from the study area,we derive the following conclusions.①Compared with granite in this area,quartz porphyry is more acidic,and the average contents of TiO2、P2O5、MnO are relatively low.The rock is Alkali-rich and potassic-rich,belonging to caic-alkaline series with complete fractional crystallization and high oxygen fugacity during rocks' formulation.According to the computation of CIPW,the standard minerals of quartz porphyry are quartz,albite.anorthite and orthoclase.The accessory minerals are diopside,corundum,hypersthene、ilmenite,magnetite ores,and apatite.While generally the content of corundum is comparatively higher than others.②The content of Au is higher than that of the strata of the Taihua Group and Xiong'er Group in the study area,as well as the three granite rock mass of Wuzhangshan,Huashan and Heyu.In comparison with primitive mantle,quartz porphyry enriches in more highly incompatible elements than weakly incompatible elements.③The content of each REE and each feature parameters of REE of quartz porphyry in Leimengou are very similar to the granite rock of Huashan in this area,and ΣREE of quartz porphyry in other area is low,and the fractionation of LREE and HREE is not very obvious.Generally there is no Eu and Ce anomaly in the study area,except for the obvious positive Eu anomaly in the Dianfang mining area.