The Sr isotope ratios of barites, karst calcites, limestones and schists from four mineralisations of the Palaeozoic Moroccan Meseta were determined. The Sr isotope ratios of barites, ranging from 0.71077+/-(4) to 0.71714+/-(3), do not distinguish among the four mineralizations, indicating a common origin for the radiogenic Sr involved. This latter was derived mainly from leaching of pre-Hercynian schists during the Hercynian orogenesis. The Sr isotope ratios of Primary limestones are similar to the ratios of the associated barites, showing that these rocks underwent metamorphic recrystallisation during the Hercynian orogenesis and that the radiogenic Sr involved was derived from the same source(s) as for the barites. This conclusion also explains the isotopic signature of karst calcites in Primary limestones, which formed after limestone recrystallisation. Finally, the comparison of the Sr isotope ratios of Moroccan barites and hydrothermal Hercynian barites from Sardinia and Bavaria shows overlapping values, suggesting that the radiogenic Sr involved in the crystallisation of these minerals was mainly derived from pre-Hercynian schists. (C) 1999 Elsevier Science Limited. All rights reserved.
Strontium isotope evidence for the origin of barite from four mineralisations of the Moroccan Meseta / Castorina, Francesca; E., Di Biasio; Masi, Umberto; Tolomeo, Luigia. - In: JOURNAL OF AFRICAN EARTH SCIENCES. - ISSN 1464-343X. - STAMPA. - 29:3(1999), pp. 619-625. [10.1016/s0899-5362(99)00118-9]
Strontium isotope evidence for the origin of barite from four mineralisations of the Moroccan Meseta
CASTORINA, Francesca;MASI, Umberto;TOLOMEO, Luigia
1999
Abstract
The Sr isotope ratios of barites, karst calcites, limestones and schists from four mineralisations of the Palaeozoic Moroccan Meseta were determined. The Sr isotope ratios of barites, ranging from 0.71077+/-(4) to 0.71714+/-(3), do not distinguish among the four mineralizations, indicating a common origin for the radiogenic Sr involved. This latter was derived mainly from leaching of pre-Hercynian schists during the Hercynian orogenesis. The Sr isotope ratios of Primary limestones are similar to the ratios of the associated barites, showing that these rocks underwent metamorphic recrystallisation during the Hercynian orogenesis and that the radiogenic Sr involved was derived from the same source(s) as for the barites. This conclusion also explains the isotopic signature of karst calcites in Primary limestones, which formed after limestone recrystallisation. Finally, the comparison of the Sr isotope ratios of Moroccan barites and hydrothermal Hercynian barites from Sardinia and Bavaria shows overlapping values, suggesting that the radiogenic Sr involved in the crystallisation of these minerals was mainly derived from pre-Hercynian schists. (C) 1999 Elsevier Science Limited. All rights reserved.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
