Spinels of Variscan olivine hornblendites related to the Montnegre granitoids revisited (NE Spain): petrogenetic evidence of mafic magma mixing
Olivine hornblendites (cortlandtites) form part of the Montnegre mafic complex related to late-Variscan I-type granitoids in the Catalan Coastal Ranges. Two generations of spinel are present in these hornblendites: Spl1 forms euhedral crystals included in both olivine and Spl2. Spl2 forms euhedral...
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| Format: | Article |
| Language: | English |
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Universitat de Barcelona (UB), Geociències Barcelona (Geo3BCN), Institut de Diagnosi Ambiental i Estudis de l'Aigua (IDAEA), Universitat Autònoma de Barcelona (UAB)
2017-11-01
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| Series: | Geologica Acta |
| Subjects: | |
| Online Access: | https://revistes.ub.edu/index.php/GEOACTA/article/view/18664 |
| _version_ | 1797654599397539840 |
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| author | G. GALÁN P. ENRIQUE L. BUTJOSA M. FERNÁNDEZ-ROIG |
| author_facet | G. GALÁN P. ENRIQUE L. BUTJOSA M. FERNÁNDEZ-ROIG |
| author_sort | G. GALÁN |
| collection | DOAJ |
| description |
Olivine hornblendites (cortlandtites) form part of the Montnegre mafic complex related to late-Variscan I-type granitoids in the Catalan Coastal Ranges. Two generations of spinel are present in these hornblendites: Spl1 forms euhedral crystals included in both olivine and Spl2. Spl2 forms euhedral to anhedral crystals associated with phlogopite and fibrous colourless amphibole forming pseudomorphs after olivine. Compositions of Spl1 are picotite-Al chromite (Fe#: 77.78-66.60; Cr#: 30.12-52.22; Fe3+/R3+: 6.99-21.89; 0.10< TiO2%< 0.62). Compositions of Spl2 are pleonaste (Fe#: 37.86-52.12; Cr#: 1.00-15.45; Fe3+/R3+: 0.31-5.21; TiO2% <0.10%). The two types of spinel follow a CrAl trend, mainly due to the substitution (Fe2+)-1Cr-1= MgAl, which is interpreted as the result of mixing between two different mantle-derived melts. The compositions of early Spl1 crystals included in olivine are characteristic of Al-rich basalts. More aluminous Spl2 would result from reaction of olivine with a less evolved, Al and K-rich mantle-derived melt after new refilling of the magma chamber or channel. As a whole, spinels from similar examples of Variscan olivine hronblendites also follow a CrAl trend with high Fe# and starting at higher Cr# than other trends of this type. Cr# heterogeneity in the early spinels from these Variscan hornblendites would be inherited from the variable Al content of the mafic melts involved in their genesis.
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| first_indexed | 2024-03-11T17:01:51Z |
| format | Article |
| id | doaj.art-f6ab48c5e7944977b3e2c01cae9b29f6 |
| institution | Directory Open Access Journal |
| issn | 1696-5728 |
| language | English |
| last_indexed | 2024-03-11T17:01:51Z |
| publishDate | 2017-11-01 |
| publisher | Universitat de Barcelona (UB), Geociències Barcelona (Geo3BCN), Institut de Diagnosi Ambiental i Estudis de l'Aigua (IDAEA), Universitat Autònoma de Barcelona (UAB) |
| record_format | Article |
| series | Geologica Acta |
| spelling | doaj.art-f6ab48c5e7944977b3e2c01cae9b29f62023-10-20T07:24:30ZengUniversitat de Barcelona (UB), Geociències Barcelona (Geo3BCN), Institut de Diagnosi Ambiental i Estudis de l'Aigua (IDAEA), Universitat Autònoma de Barcelona (UAB)Geologica Acta1696-57282017-11-01154Spinels of Variscan olivine hornblendites related to the Montnegre granitoids revisited (NE Spain): petrogenetic evidence of mafic magma mixingG. GALÁN0P. ENRIQUE1L. BUTJOSA2M. FERNÁNDEZ-ROIG3Universitat Autònoma de BarcelonaUniversitat de BarcelonaUniversitat de BarcelonaUniversitat Autònoma de Barcelona Olivine hornblendites (cortlandtites) form part of the Montnegre mafic complex related to late-Variscan I-type granitoids in the Catalan Coastal Ranges. Two generations of spinel are present in these hornblendites: Spl1 forms euhedral crystals included in both olivine and Spl2. Spl2 forms euhedral to anhedral crystals associated with phlogopite and fibrous colourless amphibole forming pseudomorphs after olivine. Compositions of Spl1 are picotite-Al chromite (Fe#: 77.78-66.60; Cr#: 30.12-52.22; Fe3+/R3+: 6.99-21.89; 0.10< TiO2%< 0.62). Compositions of Spl2 are pleonaste (Fe#: 37.86-52.12; Cr#: 1.00-15.45; Fe3+/R3+: 0.31-5.21; TiO2% <0.10%). The two types of spinel follow a CrAl trend, mainly due to the substitution (Fe2+)-1Cr-1= MgAl, which is interpreted as the result of mixing between two different mantle-derived melts. The compositions of early Spl1 crystals included in olivine are characteristic of Al-rich basalts. More aluminous Spl2 would result from reaction of olivine with a less evolved, Al and K-rich mantle-derived melt after new refilling of the magma chamber or channel. As a whole, spinels from similar examples of Variscan olivine hronblendites also follow a CrAl trend with high Fe# and starting at higher Cr# than other trends of this type. Cr# heterogeneity in the early spinels from these Variscan hornblendites would be inherited from the variable Al content of the mafic melts involved in their genesis. https://revistes.ub.edu/index.php/GEOACTA/article/view/18664Catalan Coastal RangesOlivine hornblenditesSpinel compositionsMantle-derived melts. |
| spellingShingle | G. GALÁN P. ENRIQUE L. BUTJOSA M. FERNÁNDEZ-ROIG Spinels of Variscan olivine hornblendites related to the Montnegre granitoids revisited (NE Spain): petrogenetic evidence of mafic magma mixing Geologica Acta Catalan Coastal Ranges Olivine hornblendites Spinel compositions Mantle-derived melts. |
| title | Spinels of Variscan olivine hornblendites related to the Montnegre granitoids revisited (NE Spain): petrogenetic evidence of mafic magma mixing |
| title_full | Spinels of Variscan olivine hornblendites related to the Montnegre granitoids revisited (NE Spain): petrogenetic evidence of mafic magma mixing |
| title_fullStr | Spinels of Variscan olivine hornblendites related to the Montnegre granitoids revisited (NE Spain): petrogenetic evidence of mafic magma mixing |
| title_full_unstemmed | Spinels of Variscan olivine hornblendites related to the Montnegre granitoids revisited (NE Spain): petrogenetic evidence of mafic magma mixing |
| title_short | Spinels of Variscan olivine hornblendites related to the Montnegre granitoids revisited (NE Spain): petrogenetic evidence of mafic magma mixing |
| title_sort | spinels of variscan olivine hornblendites related to the montnegre granitoids revisited ne spain petrogenetic evidence of mafic magma mixing |
| topic | Catalan Coastal Ranges Olivine hornblendites Spinel compositions Mantle-derived melts. |
| url | https://revistes.ub.edu/index.php/GEOACTA/article/view/18664 |
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