The geochemistry of potassic lavas from Vulsini, central Italy and implications for mantle enrichment processes beneath the Roman region

Rogers, Nick; Hawkesworth, Chris J.; Parker, R. J.; Marsh, Julian S

doi:10.1007/bf00378265

Cited by 284 publications

(107 citation statements)

References 40 publications

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“…It is defined as a leucite basanite, with high MgO (13.5 wt%) and CaO (13.8 wt%) contents (Table 2), closely similar to the LBSN samples described by other authors (Rogers et al 1985;Coltorti et al 1991;Conticelli and Peccerillo 1992). The phenocrysts (up to 4 mm in size) are olivine, rare Crspinel and clinopyroxene.…”

Section: Geological Setting and Sample Descriptionsupporting

confidence: 66%

“…On the other hand, Appleton (1972) considered the parental magmas to be certainly more basic than the most primitive rocks. It has to be noted that these rocks may be aphyric (e.g., Civetta et al 1984) to slightly porphyric or most likely cumulative (e.g., rocks with MgO ~ 14 wt%) and that only HKS primitive rocks were recognized in the Vulsini area (Rogers et al 1985;Civetta et al 1984;Coltorti et al 1991;Peccerillo 1992, Cioni 1993). Conversely, in the other parts of the RCP, (e.g., Roccamonfina, Appleton 1972; Giannetti and Ellain 1994; or Ernici, Civetta et al 1981), the rocks with high Mg # have been found to belong to the KS group only.…”

Section: Mineralogymentioning

confidence: 99%

“…The northern part of this province offers a large compositional spectrum of volcanic rocks, from potassic (KS) and high potassic (HKS) series (Appleton 1972;Civetta et al 1981;Peccerillo et al 1984;Rogers et al 1985;Giannetti and Ellam 1994) to strongly Si-undersaturated larnite-normative rocks (Kamafugite; Peccerillo et al 1988). The HKS group (K20/Na20 > 2; K20 > 3 wt%) includes Si-undersaturated rocks, from leucite basanite-tephritic leucitite to phonolite.…”

Section: Introductionmentioning

confidence: 99%

“…The HKS and KS series are closely associated in time and space (Appleton 1972;Civetta et al 1981;Conticelli and Peccerillo 1992;Giannetti and Ellam 1994). Low-pressure crystal fractionation has generally been invoked to account for the evolution within a series (Appleton 1972;Civetta et al 1981;Holm 1982;Peccerillo et al 1984;Rogers et al 1985), with possible additional processes such as crustal assimilation (Civetta et al 1984;Conticelli et al 1991), and magma mixing (Ferrara et al 1986;Varekamp and Kalamarides 1989).…”

Section: Introductionmentioning

confidence: 99%

“…The most primitive rocks of the RCP, and in particular, of the Vulsini area are considered by many authors as representative of near-primary melts Varekamp 1979;Rogers et al 1985;Varekamp and Kalamarides 1989;Coltorti et al 1991;Conticelli and Peccerillo 1992), mainly based on such parameters as Mg #, Ni and Cr values, traditionally thought to be the reliable criteria of the primitiveness (e.g., Frey et al 1978). However, this is not always a sufficient argument for proving the primary nature of the melt, especially taking into account the fact that highly potassic melts probably cannot be derived from the mantle of a typical peridotite composition (Foley 1992a).…”

Section: Introductionmentioning

confidence: 99%

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Potassic primary melts of vulsini (Roman Province): evidence from mineralogy and melt inclusions

Kamenetsky

Métrich²,

Cioni

1995

Contrib Mineral Petrol

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The origin and the relationships between the high potassic (HKS) and potassic (KS) suites of the Roman Comagmatic Province and the nature of their primary magmas have been intensively debated over the past 35 years. We have addressed these problems by a study of mineralogy (olivine Fo92-87, Cr-spinel and diopside) and melt inclusions in olivine phenocrysts from a scoria sample of Montefiascone (Vulsini area). This rock is considered as one of the most primitive (MgO = 13.5 wt%, NiO = 340 ppm; Cr = 1275 ppm) in the northern part of the Roman Comagmatic Province. The compositions of both the olivine and their melt inclusions are controlled by two main processes. In the case of the olivine Fo < 90.5, fractional crystallization (olivine + diopside + minor spinel) was the principal mechanism of the magma evolution. The olivine (Fo92 90.5) and the Cr-spinel (Cr# = 100. Cr/(Cr + A1)--63 73) represent a near-primary liquidus assemblage and indicate the mantle origin of their parental magmas. The compositions of melt inclusions in these olivine phenocrysts correspond to those of poorly fractionated H20-rich ( ~ 1 wt%) primary melts (MgO = 8.4-9.7 wt%, FeO t~ 6 7.5 wt%). They evidence a wide compositional range (in wt%: SiO2 = 46.5 50, K20 = 5.3-2.8, P205 = 0.4-0.2, S=0.26 0.12; C1=0.05 0.03, and CaO/A1203--0.8-1.15), with negative correlations between SiO2 and K20, A1203 and CaO, as well as positive correlations between K20, and P2Os, S, C1, with nearly constant

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Section: Geological Setting and Sample Descriptionsupporting

confidence: 66%

Section: Mineralogymentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Potassic primary melts of vulsini (Roman Province): evidence from mineralogy and melt inclusions

Kamenetsky

Métrich²,

Cioni

1995

Contrib Mineral Petrol

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Potassic alkaline granitoid magmatism in the northern margin of the Tarim Craton: First evidence of a back‐arc extensional environment

Chen

Yang

2019

Geological Journal

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The tectonic setting of the northern Tarim Craton during the Palaeozoic is vital to our understanding of the subduction polarity of the paleo-oceanic plates in the Tianshan Orogen and the accretion history of the south-western Central Asian Orogenic Belt.We first identified granitoids intruding the Palaeoproterozoic metamorphic rocks in the Kurchu area in the northern Tarim Craton. The zircon LA-ICP-MS U-Pb dating of this rock indicates that its crystallization age is 418 Ma, highlighting a late Early Palaeozoic magmatic event. Compared with the contemporaneous granitoids in the southern margin of the Tarim Craton, the Kurchu granitoid has high K 2 O (6.17-7.25 wt.%) and high alkaline (Na 2 O + K 2 O = 9.48-10.56 wt.%) contents. The Rittmann index (σ) ranges from 3.53 to 5.68, and samples plot in the shoshonite series in the K 2 O-SiO 2 diagram, indicating that the rock is a potassic-alkaline granite (PAG). In addition, this granitoid shows high REE concentrations (264-817 ppm) with significant Eu anomalies and is depleted in Ba, Sr, Nb, Ta, Ti, and P but enriched in Zr and Hf. These geochemical characteristics and high ( 87 Sr/ 86 Sr) i (0.70857-0.70995) and low εNd(T) (−10.67 to −10.24) values of the Kurchu PAG indicate that this rock was derived from the partial melting of the crust. The diagenetic conditions of the Kurchu PAG are high temperatures, as recorded by higher zircon saturation temperatures (855-919°C), low diagenetic pressure, a less shallow emplacement depth recorded by lower Sr (<200 ppm) concentrations, and a low oxygen fugacity recorded by lower Eu* (0.17-0.89), higher Zr (>355 ppm) and Hf (>9.73 ppm) concentrations, and trace element contents of zircons. In various discrimination diagrams, all samples consistently plot in rift-related areas. These geochemical and diagenetic features suggest that this magmatic event probably occurred in a backarc environment. Therefore, there is back-arc basin occurring in the northern TarimCraton in the Early Palaeozoic, which provides strong evidence that this region was an active margin probably much earlier than Silurian, necessitating the southward subduction of the South Tianshan Ocean.

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Neoarchean arc magmatism and Paleoproterozoic granulite‐facies metamorphism in the Bhavani Suture Zone, South India

et al. 2019

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The Bhavani Suture Zone in the Southern Granulite Terrane marks the zone of amalgamation of the Neoarchean Nilgiri Block and the northwestern Madurai Block in southern India. Here, we report detailed petrological, geochemical, and geochronological data on the Mettupalayam mafic-ultramafic complex within this suture zone with a view to evaluate the tectonothermal history of the Bhavani Suture Zone and adjoining crustal blocks. The metamorphosed complex includes charnockite, hornblendebiotite gneiss, mafic granulite, amphibolite, garnet-bearing mafic granulite, and dioritic gneiss along with metamorphosed banded iron formation. The mafic granulite and the dioritic gneiss occur as concordant layers of varying thickness within the hornblendebiotite gneiss. The salient geochemical features of the mafic granulite and the dioritic gneiss including the enrichment of large-ion lithophile elements and depletion of highfield-strength elements suggest a subduction-related arc magmatic setting. However, the amphibolites show MORB-related affinity, suggesting its formation from a N-MORB-related source and their accretion together with the overlying banded iron formation. The peak metamorphic conditions of the garnet-bearing mafic granulite were estimated using conventional geothermobarometers as 800-820°C/8.5-9.2 kbar, which we further confirm through phase equilibrium modelling in the Na 2 O-CaO-K 2 O-FeO-MgO-Al 2 O 3 -SiO 2 -H 2 O-TiO 2 -Fe 2 O 3 (NCKFMASHTO) system. Magmatic zircons with high Th/U ratio from the amphibolite display a well-defined discordia with an upper intercept age of 2,600 ± 38 Ma. Zircon grains from the dioritic gneiss show weighted mean 206 Pb/ 207 Pb age of 2,524 ± 6 Ma from concordant zircon spots and a comparable upper intercept age of 2,562 ± 34 Ma from discordant zircon spots, indicating protolith emplacement related to Neoarchean arc magmatism as inferred from our geochemical data. The thin overgrowth rims around the magmatic zircon grains in the amphibolite yielded an upper intercept age of 2,520 ± 20 Ma, which is comparable with the protolith crystallization age of the dioritic gneiss. Slightly younger weighted mean 207 Pb/ 208 Pb ages of 2,463 ± 27 Ma (from dioritic gneiss) and 2,422 ± 30 Ma (from amphibolite) are also obtained from the metamorphic zircon rims. These ages are correlated to the timing of high-grade metamorphism associated with final collision of the Nilgiri Block and the northwestern Madurai Block. Similar Neoarchean-Paleoproterozoic magmatism and high-grade metamorphism were

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The geochemistry of potassic lavas from Vulsini, central Italy and implications for mantle enrichment processes beneath the Roman region

Cited by 284 publications

References 40 publications

Potassic primary melts of vulsini (Roman Province): evidence from mineralogy and melt inclusions

Potassic primary melts of vulsini (Roman Province): evidence from mineralogy and melt inclusions

Potassic alkaline granitoid magmatism in the northern margin of the Tarim Craton: First evidence of a back‐arc extensional environment

Neoarchean arc magmatism and Paleoproterozoic granulite‐facies metamorphism in the Bhavani Suture Zone, South India

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