Introduction to Archean Rare-Metal Pegmatites

Dittrich, Thomas; Seifert, Thomas; Schulz, Bernhard; Hagemann, Steffen; Gerdes, Axel; Pfänder, Jörg A.

doi:10.1007/978-3-030-10943-1_1

Cited by 2 publications

(1 citation statement)

References 72 publications

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“…Lithium-cesium-tantalum (LCT) pegmatites are formed from highly fractionated melts (Černý, 1991) and dominate global lithium (Li) production (U.S. Geological Survey, 2023). LCT pegmatites first appeared in the Neoarchean (c. 2.8 Ga), are dominantly hosted in greenschist-to amphibolite-grade supracrustal rocks (Dittrich et al, 2019), and retain geochemical signatures which imply their genesis involved reworking of existing (typically metasedimentary) crust (Černý, 1991). However, fundamental questions remain regarding how these evolved rocks become highly concentrated in Li, since the primary extractable Li ore minerals -the Lialuminosilicates spodumene and petalite -only crystallize when melt Li contents exceed 5000 ppm (London, 1984;Maneta et al, 2015), representing an enrichment of ca.…”

Section: Introductionmentioning

confidence: 99%

The formation of lithium-rich pegmatites through multi-stage melting

Koopmans,

Martins,

Linnen

et al. 2023

Geology

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Lithium-cesium-tantalum−type pegmatites (the primary source of lithium) crystallize from highly evolved, volatile felsic melts that incorporated crustal material in their source. Pegmatites are classically thought to form either from extreme fractionation of a parental granite body or via low-degree partial melting of a metamorphic rock (anatectic origin). However, the processes that lead to the formation of economic lithium pegmatite deposits remain enigmatic, because precipitation of lithium ore minerals requires melt lithium concentrations in excess of 5000 ppm—∼500 times upper crustal abundances. We use petrological modeling to quantify lithium enrichment in an anatectic-origin scenario and show that it is primarily driven by the relative stability of residual biotite and muscovite at medium to high pressures (∼8 kbar), and biotite and cordierite at low pressures (∼3 kbar). We show anatexis of an average lithium-enriched metasedimentary source cannot sufficiently elevate the lithium content of the ensuing melt to form economic deposits; however, if this first-generation melt—now crystallized as granitic crust—is re-melted, the second-generation melt will be sufficiently concentrated in lithium to crystallize lithium ore minerals. We propose a petrogenetic model for anatectic-origin lithium pegmatites, in which a region experiences at least two stages of partial melting, ultimately generating lithium-rich melts without invoking extensive fractional crystallization. This mechanism can both account for the occurrence of unzoned lithium pegmatites and explain why economic pegmatites in many terranes are younger than their inferred source granites.

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Section: Introductionmentioning

confidence: 99%

The formation of lithium-rich pegmatites through multi-stage melting

Koopmans,

Martins,

Linnen

et al. 2023

Geology

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Lithium: critical, or not so critical?

Gardiner,

Jowitt,

Sykes

2024

Geoenergy

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Some metals necessary to deliver renewable energy are considered critical. Metal criticality is a major factor in achieving energy decarbonisation, leading to efforts to make metals uncritical . Among the most critical is lithium. Like many critical metals, lithium represents a small-scale market experiencing significant demand increase causing price and supply volatility, and hindering necessary transformative investment. Global lithium demand is soaring, with current supply now dominated by pegmatite-sourced lithium hydroxide. Clay extraction has yet to be industrially proven, thus there remains uncertainty from where and in what quantity future lithium supply will come, and whether lithium remains critical, however geoscience research is best focused on pegmatite and clay-sourced lithium to improve discovery and extraction. Of five lithium criticality scenarios (business as usual; clays onstream; everything plus recycling; shift away from lithium; black swan event), only two project a longer-term criticality reduction. However, few metals will be critical over the very long term as techno-economic and ESG challenges can be overcome and/or metal demand will be structurally adjusted by substitution. Although criticality may be a short to medium term barrier to the energy transition, effective research and overall market forces will reduce the majority of mineral criticality over the longer term. Thematic collection: This article is part of The energy-critical metals for a low carbon transition collection available at: https://www.lyellcollection.org/topic/collections/critical-metals

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Introduction to Archean Rare-Metal Pegmatites

Cited by 2 publications

References 72 publications

The formation of lithium-rich pegmatites through multi-stage melting

The formation of lithium-rich pegmatites through multi-stage melting

Lithium: critical, or not so critical?

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