A novel approach to identifying mantle-equilibrated zircon by using trace element chemistry

Ni, Ziqin; Arévalo, Ricardo; Piccoli, Philip M.; Reno, Barry L.

doi:10.1002/essoar.10503454.1

Cited by 2 publications

(2 citation statements)

References 94 publications

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“…Since this method does not rely on the La and Pr contents, it is less sensitive to presence of minute inclusions of apatite, monazite or xenotime which would flaw the LREE budget of the analysed zircon grain and lead to inaccurate estimates of Ce/Ce* (e.g. Ni et al, 2020). In the formulas, the N stands for "normalized to the chondritic values", here of Boynton (1984).…”

Section: Zircon Trace Element Compositionsmentioning

confidence: 99%

Cambro–Ordovician ferrosilicic magmatism along the northern Gondwana margin: constraints from the Cézarenque–Joyeuse gneiss complex (French Massif Central)

Couzinié¹,

Bouilhol²,

Laurent³

et al. 2022

BSGF - Earth Sci. Bull.

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It is well-acknowledged that the northern margin of the Gondwana supercontinent was affected by a major magmatic event at late Cambrian (Furongian) to early Ordovician (Tremadocian) times. However, an accurate assessment of its extent, origin, and significance is partly hampered by the incomplete characterization of the numerous gneiss massifs exposed in the inner part of the Variscan belt, as some of them possibly represent dismembered and deformed Furongian–Tremadocian igneous bodies. In this study, we document the case of the “Cézarenque–Joyeuse” gneisses in the Cévennes parautochton domain of the French Massif Central. The gneisses form decametre- to kilometre-thick concordant massifs interlayered within a pluri-kilometric sequence of mica- and quartz schists. They encompass two main petrological types: augen gneisses and albite gneisses, both typified by their blue and engulfed quartz grains with the augen facies differing by the presence of centimetre-sized pseudomorphs after K-feldspar and the local preservation of igneous textures. Whole-rock geochemistry highlights that many gneisses have magmatic ferrosilicic (acidic with anomalously high FeOt and low CaO) compositions while others are akin to grauwackes. Collectively, it is inferred that the bulk of the Cézarenque–Joyeuse gneisses represent former rhyodacite lava flows or ignimbrites and associated epiclastic tuffs. Volumetrically subordinate, finer-grained, and strongly silicic leucogneisses are interpreted as microgranite dykes originally intrusive within the volcanic edifices. LA–ICP–MS U–Pb dating of magmatic zircon grains extracted from an augen gneiss and a leucogneiss brackets the crystallization age of the silicic magmas between 486.1±5.5 Ma and 483.0±5.5 Ma which unambiguously ties the Cézarenque–Joyeuse gneisses to the Furongian–Tremadocian volcanic belt of SW Europe. Inherited zircon date distributions, Ti-in-zircon and zircon saturation thermometry demonstrate that they formed by melting at 750–820 °C of Ediacaran sediments. Zircon Eu/Eu* and Ce/Ce* systematics indicate that the melts were strongly reduced (fO2 probably close to the values expected for the iron–wustite buffer), possibly because they interacted during ascent with Lower Cambrian black shales. This would have enhanced Fe solubility in the melt phase and may explain the peculiar ferrosilicic signature displayed by many Furongian–Tremadocian igneous rocks in the northern Gondwana realm. We infer that crustal melting resulted from a combination of mantle-derived magma underplating in an extensional environment and anomalously elevated radiogenic heat production within the Ediacaran sedimentary sequences.

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Section: Zircon Trace Element Compositionsmentioning

confidence: 99%

Cambro–Ordovician ferrosilicic magmatism along the northern Gondwana margin: constraints from the Cézarenque–Joyeuse gneiss complex (French Massif Central)

Couzinié¹,

Bouilhol²,

Laurent³

et al. 2022

BSGF - Earth Sci. Bull.

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“…Zircon affected by post-crystallization hydrothermal alteration have murky or fluid inclusion-rich pitted textures (cf., Hoskin, 2005;Jiang et al, 2019) and/or flat chondrite-normalized LREE patterns and small Ce anomalies (Hoskin, 2005;Zhong et al 2018). Zircon that contains tiny inclusions of LREE-rich minerals (e.g., allanite, chevkinite) or fluid inclusions also have elevated La values atypical of magmatic zircon (Hoskin and Schaltegger, 2003;Claiborne et al, 2010;Ni et al, 2020). Oki-Dōzen zircon with these textural or compositional features were removed from the data set leaving only unaltered primary magmatic grains.…”

Section: Zircon U-th-pb Shrimp Geochronologymentioning

confidence: 99%

Zircon geochronological and geochemical insights into pluton building and volcanic-hypabyssal-plutonic connections: Oki-Dōzen, Sea of Japan - a complex intraplate alkaline volcano

Scarrow¹,

Chamberlain²,

Montero³

et al. 2021

msam

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The relationship between plutonic and volcanic components of magmatic plumbing systems continues to be a question of intense debate. The Oki-Dōzen Islands, Sea of Japan, preserve outcrops of temporally associated plutonic, hypabyssal and volcanic rocks. Post-intrusion uplift juxtaposed Miocene syenites in inferred faulted contact with volcanic trachytes that are cut by rhyolite hypabyssal dikes. This provides a window deep into timing and origins of magma storage architecture and dynamics. Zircon is ubiquitous in all samples; our aim is to determine what its age and composition can reveal about the plutonic-volcanic connection. Here we show magma source characteristics are recorded in zircon Hf isotopes; source composition and assimilation of heterogeneous hydrothermally altered crust in zircon O isotopes; and extensive fractional crystallization in zircon trace elements. Combined with new U-Th-Pb SHRIMP zircon ages, 6.4-5.7 Ma, compositional data show pluton formation was by protracted amalgamation of discrete magma pulses. The rhyolite dike preserves an evolved fraction segregated from these discrete magmas. Synchronous with plutonism was volcanic eruption of trachyte magma derived from the same source, which may have stalled at a relatively shallow depth prior to eruption. Stalling occurred at least above the amphibole stability zone because amphibole-compatible Sc and Ti were not depleted in the trachyte melt resulting in elevated values of these in volcanic compared to plutonic zircon. Identifying smaller episodic magma pulses in a larger magmatic complex places constraints on potential magma fluxes and eruptible volumes. High-flux, large volume, plume-related ocean island magmatic systems may have extensive vertically distributed multi-stage magmatic reservoirs and subduction-related systems transcrustal magma reservoirs. By contrast, Oki-Dōzen was a low-flux system with incremental pluton growth and small-to moderate-scale eruptions.

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A novel approach to identifying mantle-equilibrated zircon by using trace element chemistry

Cited by 2 publications

References 94 publications

Cambro–Ordovician ferrosilicic magmatism along the northern Gondwana margin: constraints from the Cézarenque–Joyeuse gneiss complex (French Massif Central)

Cambro–Ordovician ferrosilicic magmatism along the northern Gondwana margin: constraints from the Cézarenque–Joyeuse gneiss complex (French Massif Central)

Zircon geochronological and geochemical insights into pluton building and volcanic-hypabyssal-plutonic connections: Oki-Dōzen, Sea of Japan - a complex intraplate alkaline volcano

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