Sr and Nd isotope composition of the metamorphic, sedimentary and ultramafic xenoliths of Lanzarote (Canary Islands): Implications for magma sources

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• 作者：Alfredo Aparicio ; Colombo C.G. Tassinari ; Roberto Garcí ; a ; Vicente Arañ ; a
• 关键词：ultramafic– ; metamorphic xenoliths ; contact metamorphism ; Nd and Sr isotopic anomalies ; Lanzarote
• 刊名：Journal of Volcanology and Geothermal Research
• 出版年：2010
• 出版时间：1 January 2010
• 年：2010
• 卷：189
• 期：1-2
• 页码：143-150
• 全文大小：730 K

文摘

The lavas produced by the Timanfaya eruption of 1730–1736 (Lanzarote, Canary Islands) contain a great many sedimentary and metamorphic (metasedimentary), and mafic and ultramafic plutonic xenoliths. Among the metamorphosed carbonate rocks (calc-silicate rocks [CSRs]) are monomineral rocks with forsterite or wollastonite, as well as rocks containing olivine ± orthopyroxene ± clinopyroxene ± plagioclase; their mineralogical compositions are identical to those of the mafic (gabbros) and ultramafic (dunite, wherlite and lherzolite) xenoliths. The ⁸⁷Sr/⁸⁶Sr (around 0.703) and ¹⁴³Nd/¹⁴⁴Nd (around 0.512) isotope ratios of the ultramafic and metasedimentary xenoliths are similar, while the ¹⁴⁷Sm/¹⁴⁴Nd ratios show crustal values (0.13–0.16) in the ultramafic xenoliths and mantle values (0.18–0.25) in some CSRs. The apparent isotopic anomaly of the metamorphic xenoliths can be explained in terms of the heat source (basaltic intrusion) inducing strong isotopic exchange (⁸⁷Sr/⁸⁶Sr and ¹⁴³Nd/¹⁴⁴Nd) between metasedimentary and basaltic rocks. Petrofabric analysis also showed a possible relationship between the ultramafic and metamorphic xenoliths.