Strontium isotope systematics for plagioclase of the Skaergaard intrusion (East Greenland): A window to crustal assimilation, differentiation, and magma dynamics

Hagen‐Peter, Graham; Tegner, Christian; Lesher, Charles E.

doi:10.1130/g45639.1

Cited by 22 publications

(22 citation statements)

References 20 publications

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“…The ca. 55-Ma (million year)-old Skaergaard layered intrusion is a fault-controlled igneous body made up of layered gabbro (20)(21)(22)(23)(24)(25)(26) (Fig. 2A) emplaced at a depth of about 2 km within the East Greenland volcanic rifted margin.…”

Section: Skaergaard Layered Intrusionmentioning

confidence: 99%

“…1) to determine magma emplacement rates that best reproduce observations such as the width of contact metamorphic aureoles or the absence of internal contacts (17)(18)(19). Here, we explore a simple and straightforward thermal approach to obtain the first rigorous estimates of the growth rate of the Skaergaard layered intrusion, Eastern Greenland-a classic example of a solidified basaltic magma chamber, whose study has, historically, constrained many of the fundamental principles of igneous petrology (20)(21)(22)(23)(24)(25).…”

Section: Introductionmentioning

confidence: 99%

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Catastrophic growth of totally molten magma chambers in months to years

et al. 2022

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The vertical growth rate of basaltic magma chambers remains largely unknown with available estimates being highly uncertain. Here, we propose a novel approach to address this issue using the classical Skaergaard intrusion that started crystallizing from all margins inward only after it had been completely filled with magma. Our numerical simulations indicate that to keep the growing Skaergaard magma chamber completely molten, the vertical growth rate must have been on the order of several hundreds to a few thousands of meters per year, corresponding to volumetric flow rates of tens to hundreds of cubic kilometers per year. These rates are several orders of magnitude higher than current estimates and were likely achieved by rapid subsidence of the floor rocks along faults. We propose that the Skaergaard is a plutonic equivalent of supereruptions or intrusions that grow via catastrophically rapid magma emplacement into the crust, producing totally molten magma chambers in a matter of a few months to dozens of years.

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Section: Skaergaard Layered Intrusionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Catastrophic growth of totally molten magma chambers in months to years

et al. 2022

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“…Examples of mafic intrusions within mafic wallrocks are known from several LIPs worldwide (e.g., Habekost and Wilson 1989;Miller and Ripley 1996;Shellnutt 2014). For example, the Skaergaard layered intrusion in eastern Greenland has traditionally been considered to represent a largely closed-system event (e.g., Nielsen 2004), regardless of some indications of minor assimilation of Archean gneisses (e.g., Stewart and DePaolo 1990;McBirney and Creaser 2003;Hagen-Peter et al 2019). The roof of the intrusion consists of petrogenetically associated flood basalts that have been heavily altered by hydrothermal fluids (Taylor and Forester 1979).…”

Section: Wider Implications Of the Presented Modelsmentioning

confidence: 99%

Serial interaction of primitive magmas with felsic and mafic crust recorded by gabbroic dikes from the Antarctic extension of the Karoo large igneous province

Heinonen

Luttinen

Spera

et al. 2021

Contrib Mineral Petrol

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Two subvertical gabbroic dikes with widths of ~ 350 m (East-Muren) and ≥ 500 m (West-Muren) crosscut continental flood basalts in the Antarctic extension of the ~ 180 Ma Karoo large igneous province (LIP) in Vestfjella, western Dronning Maud Land. The dikes exhibit unusual geochemical profiles; most significantly, initial (at 180 Ma) εNd values increase from the dike interiors towards the hornfelsed wallrock basalts (from − 15.3 to − 7.8 in East-Muren and more gradually from − 9.0 to − 5.5 in West-Muren). In this study, we utilize models of partial melting and energy-constrained assimilation‒fractional crystallization in deciphering the magmatic evolution of the dikes and their contact aureoles. The modeling indicates that both gabbroic dikes acquired the distinctly negative εNd values recorded by their central parts by varying degrees of assimilation of Archean crust at depth. This first phase of deep contamination was followed by a second event at or close to the emplacement level and is related to the interaction of the magmas with the wallrock basalts. These basalts belong to a distinct Karoo LIP magma type having initial εNd from − 2.1 to + 2.5, which provides a stark contrast to the εNd composition of the dike parental magmas (− 15.3 for East-Muren, − 9.0 for West-Muren) previously contaminated by Archean crust. For East-Muren, the distal hornfelses represent partially melted wallrock basalts and the proximal contact zones represent hybrids of such residues with differentiated melts from the intrusion; the magmas that were contaminated by the partial melts of the wallrock basalts were likely transported away from the currently exposed parts of the conduit before the magma–wallrock contact was sealed and further assimilation prevented. In contrast, for West-Muren, the assimilation of the wallrock basalt partial melts is recorded by the gradually increasing εNd of the presently exposed gabbroic rocks towards the roof contact with the basalts. Our study shows that primitive LIP magmas release enough sensible and latent heat to partially melt and potentially assimilate wallrocks in multiple stages. This type of multi-stage assimilation is difficult to detect in general, especially if the associated wallrocks show broad compositional similarity with the intruding magmas. Notably, trace element and isotopic heterogeneity in LIP magmas can be homogenized by such processes (basaltic cannibalism). If similar processes work at larger scales, they may affect the geochemical evolution of the crust and influence the generation of, for example, massif-type anorthosites and “ghost plagioclase” geochemical signature.

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“…After filling the approximately box shaped intrusion (≈ 8 km × 11 km × 4 km, Nielsen 2004) in several pulses the magma chamber remained closed and crystallisation of gabbroic rocks occurred simultaneously on the floor (the Layered Series), roof (the Upper Border Series), and walls (Marginal Border Series) of the chamber (Fig. 1b) (Wager and Brown 1968;Holness et al 2007Holness et al , 2015Salmonsen and Tegner 2013;Hagen-Peter et al 2019). The Layered Series and Upper Border Series meet at the so-called Sandwich Horizon (Fig.…”

Section: Geological Backgroundmentioning

confidence: 99%