The relationship between mineral composition, crystal structure and paragenetic sequence: the case of secondary Te mineralization at the Bird Nest drift, Otto Mountain, California, USA
Abstract
An unusually diverse array of 25 secondary Te oxysalt minerals has been documented from Otto Mountain, California, and 18 of these from the Bird Nest drift sublocality. A paragenetic sequence for these minerals is proposed, using observed overgrowth relationships plus spatial association data and data from other localities. Apart from Te and O, the components Pb, Cu and H are essential in the majority of the minerals. The atomic Cu/Te ratio decreases through the paragenetic sequence. This, and the occurrence of minerals with additional components such as Cl^–, CO_3^(2–), SO_4^(2–) and Fe^(3+) at an intermediate stage, suggests nonmonotonic evolution of the parent fluids, reflecting differing access to or spatial distribution of various components. For the minerals with known crystal structures, two alternative 'structural units' were identified, one consisting only of the Te^(4+) or Te^(6+) oxyanion, while the other also included small, strongly-bound cations such as Cu^(2+). The degree of polymerization for the Te oxyanion correlated with the paragenetic sequence: the monomeric tellurate anions of early minerals were replaced progressively by dimers, chains and sheet structures, which may relate to a decreasing abundance of the 'network modifying' Cu^(2+) cation, analogous to Bowen's discontinuous reaction series in igneous rock-forming silicates. No relationship was seen between paragenetic order and the larger type of structural unit, or structural complexity as defined by information content. This contrasts with results in the literature for evaporite sulfates and pegmatite phosphates. While structure–paragenesis relationships may be widespread, the exact nature of such relationships may be different for different chemical systems and different paragenetic environments.
Additional Information
© 2016 The Mineralogical Society. Received 1 February 2015; Accepted 19 May 2015. Publication date: April 1, 2016. The authors thank two anonymous reviewers for helpful suggestions which improved the manuscript. Part of this study has been funded by The Ian Potter Foundation grant 'tracking tellurium' to SJM which is gratefully acknowledged. X-ray diffraction identification of species was funded by the John Jago Trelawney Endowment to the Mineral Sciences Department of the Natural History Museum of Los Angeles County and microprobe and Raman identification were funded by a grant from the Northern California Mineralogical Association. Jerry Baird is thanked for providing the picture of frankhawthorneite on khinite.Attached Files
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Additional details
- Eprint ID
- 68524
- Resolver ID
- CaltechAUTHORS:20160620-103528733
- Ian Potter Foundation
- Natural History Museum of Los Angeles County John Jago Trelawney Endowment
- Northern California Mineralogical Association
- Created
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2016-06-20Created from EPrint's datestamp field
- Updated
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2021-11-11Created from EPrint's last_modified field