Sulfur and metal fertilization of the lower continental crust

Locmelis, Marek; Fiorentini, Marco L.; Rushmer, Tracy; Arévalo, Ricardo; Adam, John A.; Denyszyn, Steven W.

doi:10.1016/j.lithos.2015.11.028

Cited by 70 publications

(64 citation statements)

References 98 publications

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“…With its crystallization age of 200 Ma, the LBMC intrusion is much younger than the Mafic Complex (286.8 ± 0.4 Ma; Fiorentini et al, 2018) and alkaline pipes (as young as 249.1 ± 0.2 Ma; Locmelis et al, 2016). 40 Ar/ 39 Ar hornblende cooling ages near 200 Ma are known from the country rocks of the LBMC intrusion (Siegesmund et al, 2008), however most published 40 Ar/ 39 Ar ages are older.…”

Section: Discussionmentioning

confidence: 99%

A bigger tent for CAMP

Denyszyn

Fiorentini

Maas

et al. 2018

Geology

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We present new high-precision geochemical and isotopic data showing that magmas related to the Central Atlantic Magmatic Province (CAMP) were emplaced at the base of the continental crust in the Ivrea Zone of northwest Italy. These results significantly extend the known footprint of one of the largest examples of a large igneous province (LIP) on the planet. The La Balma-Monte Capio (LBMC) intrusion ranges from dunitic at the base to plagioclasebearing pyroxenitic at the top. Zircons were extracted from two samples at different levels, and dated using the chemical abrasion-isotope dilution-thermal ionization mass spectrometry (CA-ID-TIMS) U-Pb method. The two weighted-mean 206 Pb/ 238 U ages at 200.5 ± 0.3 Ma and 200.1 ± 0.5 Ma indicate a short-lived magmatic system that fractionated in place. The timing of emplacement is different from that of all other mafic-ultramafic intrusions in the Ivrea Zone and is consistent with magmatism associated with the CAMP. We suggest that exposure in the Ivrea Zone provides a unique glimpse into the presently unknown character of LIP magmas at the base of the continental crust, where the emplacement of this intrusion was facilitated by its location at a lithospheric suture.

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Section: Discussionmentioning

confidence: 99%

A bigger tent for CAMP

Denyszyn

Fiorentini

Maas

et al. 2018

Geology

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“…Peridotites exhibit amphibole-, apatite-, carbonate-, or phlogopite-rich domains, pyroxenites, hornblendites, and gabbro dikes, and dunite, wehrlite, and chromitite bands (e.g., Zanetti et al, 1999). Geochronological data (e.g., Grieco et al, 2001) and the spread in Sr and Nd bulk isotope data (Voshage et al, 1987) suggest that the mantle experienced a multistage history of melt and fluid percolation from the Devonian to the Early Jurassic, with the involvement of both mantle and crustal components (Grieco et al, 2001;Locmelis et al, 2016).…”

Section: Geological Settingmentioning

confidence: 99%

Section: Geological Settingmentioning

confidence: 99%

“…Alkaline ultramafic pipes (Garuti et al, 2001) intruded the lower crust in the Permian-Early Triassic (Locmelis et al, 2016;Fiorentini et al, 2018). Their origin is attributed to the melting of mantle domains metasomatized through the Variscan subduction and reactivated during the collapse of the Variscan belt (Locmelis et al, 2016). A suite of Late Triassic-Early Jurassic sodic and alumina-rich alkaline intrusions, ranging from calcite-clinopyroxene-bearing hornblendites (Stähle et al, 2001), CITATION: Galli, A., et al, 2019, Jurassic carbonatite and alkaline magmatism in the Ivrea zone (European Alps) related to the breakup of Pangea: Geology, v. 47, p. 199-202, https:// doi .org /10 .1130 /G45678 .1 .…”

Section: Geological Settingmentioning

confidence: 99%

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Jurassic carbonatite and alkaline magmatism in the Ivrea zone (European Alps) related to the breakup of Pangea

Galli

Grassi

Sartori

et al. 2019

Geology

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We report on pipe-like bodies and dikes of carbonate rocks related to sodic alkaline intrusions and amphibole mantle peridotites in the Ivrea zone (European Southern Alps). The carbonate rocks have bulk trace-element concentrations typical of low-rare earth element carbonatites interpreted as cumulates of carbonatite melts. Faintly zoned zircons from these carbonate rocks contain calcite inclusions and have trace-element compositions akin to those of carbonatite zircons. Laser ablation-inductively coupled plasma-mass spectrometry U-Pb zircon dating yields concordant ages of 187 ± 2.4 and 192 ± 2.5 Ma, coeval with sodic alkaline magmatism in the Ivrea zone. Cross-cutting relations, ages, as well as bulk and zircon geochemistry indicate that the carbonate rocks are carbonatites, the first ones reported from the Alps. Carbonatites and alkaline intrusions are comagmatic and were emplaced in the nascent passive margin of Adria during the Early Jurassic breakup of Pangea. Extension caused partial melting of amphibole-rich mantle domains, yielding sodic alkaline magmas whose fractionation led to carbonatite-silicate melt immiscibility. Similar occurrences in other rifts suggest that small-scale, sodic and CO 2-rich alkaline magmatism is a typical result of extension and decompressiondriven reactivation of amphibole-bearing lithospheric mantle during passive continental breakup and the evolution of magma-poor rifts.

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“…Despite the wealth of previous work in the region, limited research has been undertaken on a series of Permian-Triassic ultramafic alkaline pipes that intrude the upper part of the mafic complex and the lower portion of the Kinzigite Formation (Fiorentini et al, 2007(Fiorentini et al, , 2002(Fiorentini et al, , 2018Garuti et al, 2001;Locmelis et al, 2016;Sessa et al, 2017;Zaccarini et al, 2014). These small intrusions (<300 m in diameter) consist of amphibole-rich peridotites with minor segregations of gabbroic composition.…”

Section: Introductionmentioning

confidence: 99%

Microstructural constraints on magma emplacement and sulfide transport mechanisms

et al. 2018

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The poorly constrained nature of the physical transfer of sulfides along magmatic conduits has implications for the genesis and localization of mineral deposits as well as for understanding the large-scale mobility of volatiles and metals across different geochemical reservoirs. Our natural laboratory to address this topic is a sulfide-bearing ultramafic pipe emplaced in the deep crust of the Ivrea-Verbano Zone, northwest Italy. The pipe is composed of volatile-rich peridotite that contains disseminated, blebby, and semimassive sulfides enriched in nickel, copper, and platinum-group elements (PGEs). The integration of electron backscatter diffraction orientation data and three-dimensional (3-D) X-ray computed tomography analyses from this study indicated that (1) most of olivine crystallized upon emplacement of the magma; (2) the shape and texture of the intragranular sulfide blebs, principally hosted within the central portions of the pipe, reflect early sulfide saturation; and (3) marginal areas record higher strain compared to the cores of the pipes. The differences in the size distribution of the sulfide grains between the central and marginal areas of the pipe are due to magma emplacement dynamics. The larger sulfide aggregates forming the bulk of the Ni-Cu-PGE sulfide mineralization along the margins of the pipe are interpreted to have formed by coalescence of a large number of smaller sulfide droplets. The observed sulfide size distribution between the central and marginal areas of the Valmaggia pipe is principally due to the dynamics of the magma upon emplacement, and it locally records the role of water-and carbon dioxide-bearing volatiles in the physical entrainment of dense sulfide liquids. These processes provide a viable mechanism to transport sulfides enriched in chalcophile and siderophile metals from the upper mantle into the lower continental crust, where they may be available for later remobilization into ore systems that may form subsequently in the middle and upper crust.

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Sulfur and metal fertilization of the lower continental crust

Cited by 70 publications

References 98 publications

A bigger tent for CAMP

A bigger tent for CAMP

Jurassic carbonatite and alkaline magmatism in the Ivrea zone (European Alps) related to the breakup of Pangea

Microstructural constraints on magma emplacement and sulfide transport mechanisms

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