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91.
Thirty-nine samples of basaltic core were collected from wells 121 and 123, located approximately 1.8 km apart north and
south of the Idaho Chemical Processing Plant at the Idaho National Engineering Laboratory. Samples were collected from depths
ranging from 15 to 221 m below land surface for the purpose of establishing stratigraphic correlations between these two wells.
Elemental analyses indicate that the basalts consist of three principal chemical types. Two of these types are each represented
by a single basalt flow in each well. The third chemical type is represented by many basalt flows and includes a broad range
of chemical compositions that is distinguished from the other two types. Basalt flows within the third type were identified
by hierarchical K-cluster analysis of 14 representative elements: Fe, Ca, K, Na, Sc, Co, La, Ce, Sm, Eu, Yb, Hf, Ta, and Th.
Cluster analyses indicate correlations of basalt flows between wells 121 and 123 at depths of approximately 38–40 m, 125–128 m,
131–137 m, 149–158 m, and 183–198 m. Probable correlations also are indicated for at least seven other depth intervals. Basalt
flows in several depth intervals do not correlate on the basis of chemical compositions, thus reflecting possible flow margins
in the sequence between the wells. Multi-element chemical data provide a useful method for determining stratigraphic correlations
of basalt in the upper 1–2 km of the eastern Snake River Plain.
Received: 16 February 1996 · Accepted: 1 April 1996 相似文献
92.
Xiu-jin Liu Ke Yang Fei Guo Shi-qi Tang Ying-han Liu Li Zhang Hang-xin Cheng Fei Liu 《China Geology》2022,5(1):1-11
To illuminate the migration and transformation of selenium(Se)in the igneous rock-soil-rice system,285 pairs of rhizosphere soil and rice samples were collected from the granitoid and basalt areas in Hainan Province,South China.The contents of Se in soils derived from granitoid and basalt are,respectively,0.19±0.12 mg/kg and 0.34±0.39 mg/kg,which are much higher than Se contents in granitoid and basalt.Selenium shows remarkable enrichment from granitoid and basalt to soils.The mobile fraction of Se in soils derived from granitoid is 0.0100±0.0034 mg/kg,which is significantly higher than that of basalt(0.0058±0.0039 mg/kg).Although soil derived from basalt shows higher Se contents,Se contents in rice samples,mobile fractions of Se in soils,and biological concentration factor(BCF)is similar or even lower than that from granitoid.Basalt consist of calcic plagioclase and pyroxene,and are much richer in Fe,Al,and Ca than granitoid.Correspondingly,the basalt-derived soils have higher goethite,hematite,kaolinite,cation exchange capacity(CEC)content,and higher p H than the granitoid-derived soils,which result in higher adsorption capacity for Se and relatively lower Se bioavailability.Soils derived from granitoid and basalt in tropical regions are beneficial to produce Se-rich rice. 相似文献
93.
94.
We present new geochemical analyses of minerals and whole rocks for a suite of mafic rocks from the crustal section of the
Othris Ophiolite in central Greece. The mafic rocks form three chemically distinct groups. Group 1 is characterized by N-MORB-type
basalt and basaltic andesite with Na- and Ti-rich clinopyroxenes. These rocks show mild LREE depletion and no HFSE anomalies,
consistent with moderate degrees (~15%) of anhydrous partial melting of depleted mantle followed by 30–50% crystal fractionation.
Group 2 is represented by E-MORB-type basalt with clinopyroxenes with higher Ti contents than Group 1 basalts. Group 2 basalts
also have higher concentrations of incompatible trace elements with slightly lower HREE contents than Group 1 basalts. These
chemical features can be explained by ~10% partial melting of an enriched mantle source. Group 3 includes high MgO cumulates
with Na- and Ti-poor clinopyroxene, forsteritic olivine, and Cr-rich spinel. The cumulates show strong depletion of HFSE,
low HREE contents, and LREE enrichments. These rocks may have formed by olivine accumulation from boninitic magmas. The petrogenesis
of the N-MORB-type basalts and basaltic andesites is in excellent agreement with the melting conditions inferred from the
MOR-type peridotites in Othris. The occurrence of both N- and E-MORB-type lavas suggests that the mantle generating the lavas
of the Othris Ophiolite must have been heterogeneous on a comparatively fine scale. Furthermore, the inferred parental magmas
of the SSZ-type cumulates are broadly complementary to the SSZ-type peridotites found in Othris. These results suggest that
the crustal section may be genetically related to the mantle section. In the Othris Ophiolite mafic rocks recording magmatic
processes characteristic both of mid-ocean ridges and subduction zones occur within close spatial association. These observations
are consistent with the formation of the Othris Ophiolite in the upper plate of a newly created intra-oceanic subduction zone.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
95.
作者收集了国内外玄武岩和金伯利岩中不同产状的斜方辉石300余个样品的矿物化学资料。通过对这些资料的分析,确定了斜方辉石的成分范围区。研究表明,斜方辉石的Al_2O_3含量随压力增高而增加,但是,当压力超过21.4×10~8-24.9×10~8Pa时,Al_2O_3含量随压力的继续增高而呈减少趋势。产于金伯利岩中的斜方辉石以富Mg,100Mg/(Mg+Fe~(3+)+Fr~(2+)+Mn)值高和极贫Al、Ca为特征;产于玄武岩中的斜方辉石以贫Mg,富Ca、Fe为特点;Ⅱ型包体可能是在高压条件下从寄主岩——玄武岩中结晶出来的,与巨晶具有相似的成因。 相似文献
96.
海南岛北部玄武岩上土壤发生的化学特性研究 总被引:5,自引:0,他引:5
海南岛北部不同时期喷发的玄武岩上发育的土壤构成一个风化成土时间系列。对这一土壤系列的化学特性研究表明,随风化成土时间的增加,pH值不断下降,但至富铁土后,pH趋于稳定,而土壤CEC7,盐基饱和度下降。同时,土体中Al2O3、Fe2O3、TiO2含量增加,而Ca、Mg、K、Na淋失强烈,SiO2含量也不断降低。以土壤中大量元素含量为基础计算多数指标难以反映热带地区碱金属和碱土金属元素迅速而强烈淋失的成土风化过程。常用的土体分子硅铝率和硅铁铝率并不能指示所有土壤的风化成土作用程度。 相似文献
97.
98.
福建镇海一带玄武岩柱状节理的动力学研究:兼论柱状节理的成因 总被引:5,自引:1,他引:5
根据流体动力学和自组织理论,研究了玄武岩柱状节理形成的动力学特征,并应用福建镇海一带玄武岩平均化学成分,估算出动力学方程中所涉及的参数,求出了断面直径与节理柱体长度之间的函数关系,并用数值计算方法,求出了R_a,d和L的值,其结果与该地区的地质实际基本吻合,最后探讨了柱状节理的成因机理,并把柱状节理的形成过程划分为两个阶段:(1)热耗散-对流阶段,(2)冷却-收缩阶段。 相似文献
99.
J. P. McGreevy 《地球表面变化过程与地形》1982,7(2):189-195
Geomorphologists have not devoted sufficient attention to the formation of clay minerals by hydrothermal activity. This paper describes the breakdown of freshly-quarried basalt by cyclic wetting and drying. Breakdown is attributed to the swelling of hydrothermally-derived smectite, and it is argued that the effects of endogenic processes can exert a significant control upon weathering behaviour under earth surface conditions. 相似文献
100.
汝城地区晚中生代火山岩地球化学特征及其对源区属性的指示 总被引:4,自引:0,他引:4
湘东南汝城地区发育一套由基性玄武岩和中酸性安山质-英安质岩石组成的火山岩建造,属于低钾拉斑系列,该火山岩系中两个玄武岩的K-Ar年龄分别为124.5±2.5Ma和127.6±1.9Ma,属晚侏罗—早白垩世产物。在主、微量元素上两者成分存在明显差异。其中安山质-英安质岩石具有高MgO特征,属高MgO岩石,LILE富集、Nb-Ta、Sr-P亏损强烈,(La/Yb)N=6.7~7.9,Eu*/Eu=0.74~0.85,具岛弧型微量元素配分型式,87Sr/86Sr(t)=0.71079~0.71118,εNd(t)=-7.64~-8.16,与adakites高Mg岩石有着明显的差别,可能是富集岩石圈地幔熔融后直接分异的产物;玄武岩LILE富集,Nb-Ta富集,(La/Yb)cn=4.0~4.3,Eu*/Eu=1.00~1.16,具OIB型微量元素配分型式,87Sr/86Sr(t)=0.70812~0.70832,εNd(t)=0.48~1.03,其源区具二元混合趋势,其源区可能是富集型岩石圈地幔端员与亏损的软流圈地幔端员的混合产物。汝城地区晚中生代玄武岩和高Mg安山质-英安质岩石源区属性的限定及其相互的空间依存关系表明该区晚中生代时有着较薄的岩石圈厚度,处于岩石圈伸展减薄的大地构造背景。 相似文献