Details

Autor(en) / Beteiligte

• Loader, Matthew A.
• Wilkinson, Jamie J.
• Armstrong, Robin N.

Titel

The effect of titanite crystallisation on Eu and Ce anomalies in zircon and its implications for the assessment of porphyry Cu deposit fertility

Ist Teil von

• Earth and planetary science letters, 2017-08, Vol.472, p.107-119

Ort / Verlag

Elsevier B.V

Erscheinungsjahr

2017

Link zum Volltext

Quelle

ScienceDirect Journals (5 years ago - present)

Beschreibungen/Notizen

• The redox sensitivity of Ce and Eu anomalies in zircon has been clearly demonstrated by experimental studies, and these may represent an important tool in the exploration for porphyry Cu deposits which are thought to be derived from oxidised magmas. These deposits are significant because they are the source of much of the world's copper and almost all of the molybdenum and rhenium, key elements in many modern technologies. However, Ce and Eu anomalies in zircon are also affected by the co-crystallisation of REE bearing phases, such as titanite. Here, we report the trace element chemistry of zircons from titanite-bearing intrusions associated with mineralisation at the world class Oyu Tolgoi porphyry Cu–Au deposit (Mongolia). Based on these data, we suggest that neither zircon Eu/Eu⁎, nor Ce4+/Ce3+ are robust proxies for melt redox conditions, because they are both too strongly dependent on melt REE concentrations, which are usually poorly constrained and controlled by the crystallisation of titanite and other REE-bearing phases. In spite of this, Eu/Eu⁎ can broadly distinguish between fertile and barren systems, so may still be an indicator of porphyry magma fertility, and a useful tool for exploration. •Zircon's utility as a redox proxy is compromised by titanite co-crystallisation.•Titanite crystallisation strongly affects zircon Eu/Eu⁎ and Ce4+/Ce3+.•High zircon Yb/Gd and low Ta also result from titanite co-crystallisation.•Zircon is still a useful discriminator of barren and fertile porphyry magmas.