PreprintArticleVersion 2Preserved in Portico This version is not peer-reviewed
Implications of Hf Isotopes for the Evolution of the Mantle Source of Magmas Associated with the Giant El Teniente Cu-Mo Megabreccia Deposit, Central Chile
Version 1
: Received: 27 July 2019 / Approved: 29 July 2019 / Online: 29 July 2019 (04:20:12 CEST)
Version 2
: Received: 7 September 2019 / Approved: 8 September 2019 / Online: 8 September 2019 (17:22:48 CEST)
Stern, C.R.; Pang, K.-N.; Lee, H.-Y.; Skewes, M.A.; Arévalo, A. Implications of Hf Isotopes for the Evolution of the Mantle Source of Magmas Associated with the Giant El Teniente Cu-Mo Megabreccia Deposit, Central Chile. Minerals2019, 9, 550.
Stern, C.R.; Pang, K.-N.; Lee, H.-Y.; Skewes, M.A.; Arévalo, A. Implications of Hf Isotopes for the Evolution of the Mantle Source of Magmas Associated with the Giant El Teniente Cu-Mo Megabreccia Deposit, Central Chile. Minerals 2019, 9, 550.
Stern, C.R.; Pang, K.-N.; Lee, H.-Y.; Skewes, M.A.; Arévalo, A. Implications of Hf Isotopes for the Evolution of the Mantle Source of Magmas Associated with the Giant El Teniente Cu-Mo Megabreccia Deposit, Central Chile. Minerals2019, 9, 550.
Stern, C.R.; Pang, K.-N.; Lee, H.-Y.; Skewes, M.A.; Arévalo, A. Implications of Hf Isotopes for the Evolution of the Mantle Source of Magmas Associated with the Giant El Teniente Cu-Mo Megabreccia Deposit, Central Chile. Minerals 2019, 9, 550.
Abstract
We have determined Hf isotopic compositions of 12 samples associated with the giant El Teniente Cu-Mo deposit, Chile. The samples range in age from ≥8.9 to 2.3 Ma and provide information about the temporal evolution of their magmatic sources from the Late Miocene to Pliocene. Together with previously published data, the new analysis indicate a temporal decrease of 10 εHf(t) units, from +11.6 down to +1.6, in the 12.7 m.y. from 15 to 2.3 Ma. These variations imply increasing incorporation of continental crust through time in the magmas that formed these rocks. The fact that the samples include mantle-derived olivine basalts and olivine lamprophyres suggests that these continental components were incorporated into their mantle source, and not by intra-crustal contamination (MASH). We attribute the increase, between the Middle Miocene and Pliocene, of crustal components in the subarc mantle source below El Teniente to be due to increased subduction erosion and transport of crust into the mantle. The deposit formed above a large, long-lived, vertically zoned magma chamber that developed due to compressive deformation and persisted between the period ~7 to 4.6 Ma. Progressively more hydrous mantle-derived mafic magmas feed this chamber from below, providing heat, H2O, S and metals, but no unique “fertile” Cu-rich magma was involved in the formation of the deposit. As the volume of these mantle-derived magmas decreased from the Late Miocene into the Pliocene, the chamber crystallized and solidified, producing felsic plutons and large metal-rich magmatic-hydrothermal breccias that emplaced Cu and S into the older (≥8.9 Ma) mafic host rocks of this megabreccia deposit.
Keywords
El Teniente Cu-Mo deposit; Andean magmatism; subduction erosion; mantle source region contamination; hafnium isotopes
Subject
Environmental and Earth Sciences, Geochemistry and Petrology
Copyright:
This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
Received:
8 September 2019
Commenter:
Charles Stern
Commenter's Conflict of Interests:
Author
Comment:
We have made some revisions after a first set of reviews. These include:
1) switching the order of figures 4 and 5 and revising the new figure 5
2 adding twp tables (table 2 and 3) of major and trace-element data
3) a number of small changes to the text
Commenter: Charles Stern
Commenter's Conflict of Interests: Author
1) switching the order of figures 4 and 5 and revising the new figure 5
2 adding twp tables (table 2 and 3) of major and trace-element data
3) a number of small changes to the text