Late Cretaceous rift-related upwelling and melting of the Trindade starting mantle plume head beneath western Brazil

被引：0

作者：

S. A. Gibson

R. N. Thompson

R. K. Weska

A. P. Dickin

O. H. Leonardos

机构：

[1] Department of Earth Sciences,

[2] University of Cambridge,undefined

[3] Cambridge,undefined

[4] CB2 3EQ,undefined

[5] UK,undefined

[6] Department of Geological Sciences,undefined

[7] University of Durham,undefined

[8] Durham,undefined

[9] DHI 3LE,undefined

[10] UK,undefined

[11] Departmento de Recursos Minerais,undefined

[12] Universidade Federal de Mato Grosso,undefined

[13] Cuiabá,undefined

[14] 78.100,undefined

[15] Brazil,undefined

[16] Department of Geology,undefined

[17] McMaster University,undefined

[18] 1280 Main Street West,undefined

[19] Hamilton,undefined

[20] Ontario,undefined

[21] l8S 4M1,undefined

[22] Canada,undefined

[23] Departmento de Geoquimica e Recursos Minerais,undefined

[24] Instituto de Geociencias,undefined

[25] Universidade de Brasilia,undefined

[26] 70910 Brasilia DF,undefined

[27] Brazil,undefined

来源：

Contributions to Mineralogy and Petrology | 1997年 / 126卷

关键词：

Potential Temperature; Nepheline; Lithospheric Mantle; Mantle Plume; Mobile Belt;

D O I：

暂无

中图分类号：

学科分类号：

摘要：

High mantle potential temperatures and local extension, associated with the Late-Cretaceous impact of the Trindade mantle plume, produced substantial widespread and voluminous magmatism around the northern half of the Paraná sedimentary basin. Our previous studies have shown that, above the central and eastern portions of the postulated impact zone where lithosphere extension is minimal, heat conducted by the plume caused large-scale melting of the more fusible parts of the subcontinental lithospheric mantle beneath the margin of the São Francisco craton and the surrounding Brasilía mobile belt. Here we combine geochemical data and field evidence from the Poxoreu Igneous Province, western Brazil to show how more intense lithospheric extension above the western margin of the postulated impact zone permitted greater upwelling and melting of the Trindade plume than further east. Laser 40Ar/39Ar age determinations indicate that rift-related basaltic magmas of the Poxoreu Igneous Province were emplaced at ˜ 84 Ma. Our detailed geochemical study of the mafic magmas shows that the parental melts underwent polybaric crystal fractionation within the crust prior to final emplacement. Furthermore, some magmas (quartz-normative) appear to have assimilated upper crust whereas others (nepheline- and hypersthene-normative) appear to have been unaffected by open-system crustal magma chamber processes. Incompatible trace element ratios (e.g. chondrite-normalised La/Nb = 1) and isotopic ratios (87Sr/86Sr = 0.704 and 143Nd/144Nd = 0.51274) of the Hy-normative basalts resemble those of oceanic islands (OIB). We therefore propose that these “OIB-like” magmas were predominantly derived from convecting-mantle-source melts (i.e. Trindade mantle plume). Inverse modelling of rare-earth element (REE) abundances suggests that the initial melts were predominantly generated within the depth range of ˜80–100 km, in mantle with a potential temperature of ˜1500 °C.

引用

页码：303 / 314

页数：11