Figure 15
(A) Central zone of clay and disseminated pyrite within the zone of hydrothermal alteration in the Eastern Hohonu River; (B) 'slot' or embayment in the Little Hohonu River created by the preferential erosion of hydrothermal veins; (C) hard, brown coating on carbonate veins; and (D) shear planes in the French Creek Granite defined by streaky dark minerals. Hammer for scale.
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Alkaline igneous complexes are one of two primary sources of rare earth elements (REEs), which are unique metals crucial for the economic growth of a country. Understanding REE metallogenesis in these systems is often complicated, with evidence of both magmatic and hydrothermal processes present. The A-type French Creek Granite (FCG), located on th...
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The Saima deposit is a newly discovered niobium deposit which is located in the eastern of Liaoning Province, NE China. Its mineralization age and geochemical characteristics are firstly reported in this study. The Nb orebodies are hosted by the grey–brown to grass-green aegirine nepheline syenite. Detailed petrographical studies show that the syen...
Citations
... Based on its alkaline geochemistry and A 1 -subtype classification, Waight et al. (1998a) concluded that the French Creek Granite was derived from fractionation of an initially mantle-derived melt with oceanic island basalt (OIB)-like characteristics. Similarities in isotopic compositions and field relationships, that is, that composite dikes, felsic dikes, French Creek Granite, and Hohonu Dike Swarm all cross-cut each other indicate that the French Creek Granite and the Hohonu Table 1 as well as additional unpublished analyses from Morgenstern (2016). Location information for all samples can be found in the Petlab database (Strong et al. 2016; http://pet.gns.cri.nz). ...
The French Creek Granite, New Zealand, is an alkaline intrusion with enrichment in rare earth elements (REE). Petrography and whole-rock geochemical signatures demonstrate that the c. 82–84-Ma French Creek Granite is a composite granitoid, dominated by a ferroan, weakly peraluminous biotite alkali feldspar granite to syenogranite, with subordinate quartz-alkali feldspar (QAF) syenite. Maximum total REE + Y contents are higher in the granite and felsic dikes relative to the marginal QAF syenite, cogenetic mafic Hohonu Dike Swarm, and pegmatites. Our findings suggest that REE and high-field-strength element enrichment in the unaltered French Creek Granite is a function of partial melting from an enriched HIMU-like lithospheric mantle source, minor crustal assimilation, and extensive magmatic differentiation. Primary (magmatic) REE enrichment is defined by the occurrence of allanite, zircon, apatite, fergusonite, monazite, perrierite, and loparite, which are commonly associated with interstitial biotite. French Creek Granite samples from a phyllic-sericitic alteration zone in the Eastern Hohonu River are strongly elevated in REE relative to unaltered French Creek Granite, indicating remobilization and secondary REE enrichment by hydrothermal fluids. The REE are hosted in bastnäsite group minerals, monazite, xenotime, and zircon. Quartz protuberances, dilatational microfractures, and dike emplacement indicate that this alteration is structurally controlled. The δ13C and δ18O values of secondary carbonate veinlets are consistent with mixed low-temperature (~ 250–260 °C) magmatic hydrothermal fluids containing mantle-derived carbon. These fluids were likely part of a late-stage porphyry-type system operating during the same mantle degassing and extensional episode that was associated with the emplacement of the French Creek Granite and lamprophyric dikes of the Hohonu Dike Swarm, and initial Tasman Sea spreading. Results from this study provide an important insight into the complex processes responsible for REE enrichment in alkaline igneous systems.
... The global location of alkaline igneous rocks and carbonatites hosting significant economic REE deposits (modified from Wall, 2014); and (B) the location of plutonic rocks (purple) in the South Island of New Zealand, with alkaline igneous rocks and carbonatites, some of which are currently the most prospective for REE mineralisation (Christie et al., 2010(Christie et al., , 2011Price, 2013) and their maximum La+Ce+Y (ppm) values (Tappenden, 2003;Cooper and Paterson, 2008;Christie et al., 2010;Jongens et al., 2012;Wall, 2014;Turner, 2015;Strong et al., 2016;Morgenstern, 2016) labelled for reference. ppm: parts per million. ...
... The mineral system model presented in this study is an amalgamation of the original mineral system theory proposed by Wyborn et al. (1994) and the exploration target system later established by McCuaig et al. (2010). Our model is based on both literature review of global alkaline igneous complex-hosted and carbonatite-hosted REE deposits, and our understanding of the REE mineralisation within the A-type French Creek Granite (Fig. 1B), located on New Zealand's West Coast (Morgenstern, 2016). Each component of the intrusion-related REE mineral system was separated into critical processes, constituent processes and targeting elements. ...
The world, as we know it, is constantly changing, both physically and technologically. Technological advances and societal attitudes are currently generating a global trend towards so-called cleaner, more efficient, renewable energies and technologies, such as an increase in wind and solar power, advancements in energy saving technology, and the increasing use of electric vehicles. Essential components for these innovative “green” technologies rely on obtaining critical minerals containing key elements such as lithium for long-life batteries, rare earth elements (REEs) for magnets in hybrid cars, tungsten for wind turbines, and high-purity silicon for smart glass. To date, the scale of New Zealand’s green mineral potential has not been examined in detail; however, legacy data are available in GNS Science databases including QMAP, Petlab, GERM and REGCHEM. We are now using these databases to examine the country’s green mineral potential, along with a review of data from recent regional geophysical and geochemical surveys. By utilising these data and developing conceptual mineral system models for selected green minerals, we can identify critical steps towards locating mineral occurrences and, importantly, those that can be mapped from current data. This work will allow us to produce national- and regional-scale mineral potential and data distribution maps. We present an example of this approach for intrusion-related REE mineralisation in the South Island and show where additional data collection would enhance our knowledge of the REE potential. From these types of mineral system models, a national prospectivity framework and new exploration methodologies can be developed, and new concepts generated for future data acquisition programmes. This improved understanding of the scale and distribution of NZ’s green minerals should help attract new exploration investment, create a more prosperous and independent economy, and allow the country to play a larger role in renewable technologies research.
