Apatite: A proxy to study ore deposits?
Résumé
Apatite (Ca5(PO4)3(OH, F, Cl)) is an ubiquitous accessory
mineral found in many types of rocks and environments. This
mineral has several key features for the characterization
and/or the dating of fluid circulation or magmatism
responsible for the emplacement of mineralization:
1. It often incorporates uranium during its crystallization.
This makes it an excellent candidate for U-Pb dating.
Moreover, apatite can also be dated by the fission tracks and
(U-Th)/He methods. Therefore the same mineral can bring
information on the age of the mineralization and its
exhumation history.
2. Apatite is an excellent trap for the P, F, Cl, OH, but
also for Rare Earth Elements (REE) [1].
3. This mineral can easily react in the presence of brines,
or aqueous fluids containing CO2, HCl, H2SO4 and/or F [2].
4. In many ore deposit, the crystallization of apatite is
contemporaneous with mineralization processes [3].
5. Its closure temperature with respect to the U-Pb system
(375-550°C) gives it a peculiar role for dating hydrothermal
events [4].
Accordingly, apatite is, a priori, an excellent proxy for
obtaining extensive information about mineralizing fluids
and/or fertile magmas (temperatures, compositions and ages
or durations of the events), information that is essential for
establishing a metallogenic model.
We will present a comprehensive set of CL imaging,
EPMA analyses, SIMS stable isotopes and U-Pb dating on
apatite from several ore deposits in order to assess the
potential of this mineral for the study of ore deposits.
[1] O’Really & Griffin & (2000). Lithos, 53, 217-232. [2]
Pan & Fleet (2002). Rev in Mineral and Geochem, 48, 13-49.
[3] Nyström & Henriquez (1994). Econ. Geol. 89, 820–839.
[4] Blackburn et al. (2011). Contrib. Miner. Petrol. 162, 479–
500.