Understanding the zinc-rich mineral assemblage of the Sterling Hill deposit, New Jersey, USA
Abstract
Sterling Hill, New Jersey is a unique mineral deposit, since it hosts the largest collection of fluorescent minerals worldwide and because of its rare zinc-rich, sulfide-poor mineral assemblage. The deposit contains 350 mineral phases and is the type-locality for over two dozen of them. Zinc's economic importance and the lack of literature describing the baseline chemical behavior of zinc in many of these mineral phases are the main motivations for this study. Sterling Hill provides us with an exceptional opportunity to study zinc-rich endmembers of solid solutions, such as petedunnite and diopside-hedenbergite-johannsenite. Notably, literature data on zinc incorporation into pyroxene solid solutions is minimal; i.e., there is one study by Essene and Peacor [1] that investigates the zinc-rich clinopyroxenes of Sterling Hill. This project aims to expand further on this subject.
First analytical results on the compositional variations reveal elevated Zn contents in phases that are typically zinc-poor, e.g., pyroxene with up to 9 wt% ZnO and biotite with up to 15 wt% ZnO. Pairs of mica-gahnite, mica-amphibole, mica-willemite, mica-pyroxene, and mica-franklinite were used to obtain first-order partitioning coefficients for zinc, D(Zn). The D(Zn) range from about 0.007 for the mica-gahnite pair up to 2.7 for the mica-pyroxene pair. Except for the mica-pyroxene pair, there is a distinct positive relationship between D(Zn) and Mn/(Mn+Fe+Mg). While it is clear that Zn replaces Mn, Mg, and/or Fe in the structure of the studied mineral phases, this relationship indicates a coupled substitution mechanism such as Zn+Mn = Mg+Fe. To test this hypothesis, to better understand Zn partitioning in hydrothermal environments in general, and to constrain the conditions of the formation of the Sterling Hill deposit in particular, we will perform hydrothermal experiments in cold-seal pressure vessels. The results of these experiments will be presented at the meeting. [1] Essene et al. (1987) Am. Mineral., 72(1-2), pp.157-166.- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2018
- Bibcode:
- 2018AGUFM.V31E0173C
- Keywords:
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- 3613 Subduction zone processes;
- MINERALOGY AND PETROLOGYDE: 3654 Ultra-high pressure metamorphism;
- MINERALOGY AND PETROLOGYDE: 3656 Ultra-high temperature metamorphism;
- MINERALOGY AND PETROLOGYDE: 3660 Metamorphic petrology;
- MINERALOGY AND PETROLOGY