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New U Pb zircon age and petrogenesis of the plagiogranite, Troodos ophiolite, Cyprus

Chen, Yanhong; Niu, Yaoling; Shen, Fangyu; Gao, Yajie; Wang, Xiaohong

New U Pb zircon age and petrogenesis of the plagiogranite, Troodos ophiolite, Cyprus Thumbnail


Authors

Yanhong Chen

Yaoling Niu

Fangyu Shen

Yajie Gao

Xiaohong Wang



Abstract

The Troodos ophiolite is a classic and is one of the most complete and best-studied ophiolites on Earth. However, there are few studies on the geochronology of the plagiogranite in the Troodos ophiolite. With the advancement of zircon U-Pb in situ dating method developed in recent decades, it is necessary to revisit the age of the plagiogranite. In this study, we carried out detailed petrography, zircon U-Pb dating and mineral compositional analysis for the plagiogranite. Our new zircon ages of ~90–91 Ma confirm the previous age data. Our findings also offer new perspectives on the petrogenesis of the Troodos plagiogranite. It is common that some of the Troodos plagiogranite outcrops show intense “epidotization”. The Troodos plagiogranite can thus be divided into epidote-free plagiogranite and epidote plagiogranite. Zircons in the epidote plagiogranite have mottled texture with high contents of most elements (especially for P, Y, REEs, Nb and Ta), which differs distinctly from those in the epidote-free plagiogranite with a clean appearance and oscillatory zoning. The two types of zircons all having high Th/U ratio (0.25–1.46 with an average of 0.69) are consistent with being of magmatic origin. The texture and composition of zircons from the epidote plagiogranite suggest that they are crystallized from a highly dissolving agent that transforms existing minerals such as plagioclase and amphiboles while concentrating rare earth elements (REEs) and high field strength elements (HFSEs, including Nb, Ta, Ti, Zr, Hf, Th and U4+) to precipitate accessory minerals such as zircon and titanite as well as the more abundant epidote. The intergrowth of quartz and skeletal plagioclase together with the precipitation of zircon, titanite and epidote indicates that the highly dissolving agent is best understood as late-stage magmatic fluid or more likely supercritical fluid/melt whose nature and origin deserve further investigation.

Citation

Chen, Y., Niu, Y., Shen, F., Gao, Y., & Wang, X. (2020). New U Pb zircon age and petrogenesis of the plagiogranite, Troodos ophiolite, Cyprus. Lithos, 362-363, Article 105472. https://doi.org/10.1016/j.lithos.2020.105472

Journal Article Type Article
Acceptance Date Mar 8, 2020
Online Publication Date Mar 10, 2020
Publication Date Jun 30, 2020
Deposit Date Mar 10, 2020
Publicly Available Date Mar 28, 2024
Journal Lithos
Print ISSN 0024-4937
Publisher Elsevier
Peer Reviewed Peer Reviewed
Volume 362-363
Article Number 105472
DOI https://doi.org/10.1016/j.lithos.2020.105472

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