Please Note:

The Open Access Repository will be moving to a new authentication system on the 1st of November.

From this date onwards, account holders will be required to login using their University of Tasmania credentials.
If your current repository username differs from your University username, please email E.Prints@utas.edu.au so we can update these details on your behalf.

Due to the change, there will be a short outage of the repository from 9am on the morning of the 1st of November

Open Access Repository

Chlorine in submarine volcanic glasses from the eastern Manus basin

Downloads

Downloads per month over past year

Sun, W and Binns, RA and Fan, AC and Kamenetsky, VS and Wysoczanski, R and Wei, GJ and Hu, YH and Arculus, RJ (2007) Chlorine in submarine volcanic glasses from the eastern Manus basin. Geochimica et Cosmochimica Acta, 71 (6). pp. 1542-1552. ISSN 0016-7037

[img] PDF
GCA-2007-Manus...pdf | Request a copy
Full text restricted
Available under University of Tasmania Standard License.

Abstract

Submarine volcanic glasses from the eastern Manus Basin of Papua New Guinea, ranging from basalt to rhyodacite, clarify the geochemical behavior of Cl in arc-type magmas. For the Manus samples, Cl is well correlated with non-volatile highly incompatible trace elements, suggesting it was not highly volatile and discounting significant seawater contamination. The Cl partition coefficient is close to but slightly lower than that of Nb and K2O, a behavior similar to that in mid-ocean ridge basalts (MORB) and ocean island basalts (OIB). The similar incompatibilities of Cl and Nb imply that the Cl/Nb values of the eastern Manus Basin glasses reflect their magma source. For glasses from other west Pacific back-arc basins, Cl/Nb, Ba/Nb, and U/Nb increase towards the subduction trench, indicating increased contribution of a component enriched in Cl, Ba, and U, likely from subduction-released slab fluids. It is estimate that similar to 80% of the Cl in the Manus arc-type glasses was added directly from subducted slab-derived fluids. We have also modeled Cl behavior during magma evolution in general. Our results show that the behavior of Cl in magma is strongly influenced by pressure, initial H2O content, and the degree of magmatic fractionation. At early stages of magmatic evolution, for magmas with initial H2O content of < 4.0 wt%, Cl is highly incompatible under all pressures. By contrast, for more evolved magmas at moderately high pressure and high H2O contents, considerable amounts of Cl can be extracted from the magma once H2O saturation is reached. Accordingly, Cl is usually highly incompatible in MORB and OIB because of their low H2O contents and relatively low degrees of fractional crystallization. The behavior of Cl in arc magmas is more complicated, ranging from highly incompatible to compatible depending on H2O content and depth of magma chambers. The behavior of Cl in the eastern Manus Basin magmas is consistent with low H2O contents (1.1-1.7 wt%) and evolution at low pressures (< 0.1 GPa). Modeling results also indicate that Cl will behave differently in intrusive rocks compared to volcanic rocks because of the different pressures involved. This may have a strong influence on the mechanisms of ore genesis in these two tectonic settings.

Item Type: Article
Keywords: back-arc basin, papua-new-guinea, convergent-margin magmas, mantle-derived rocks, New Britain island-arc, laser ablation icp-ms, melt inclusions, glass, degassing, fractionation, lau basin, subduction zones, Pacmanus
Journal or Publication Title: Geochimica et Cosmochimica Acta
Page Range: pp. 1542-1552
ISSN: 0016-7037
Identification Number - DOI: 10.1016/j.gca.2006.12.003
Additional Information:

The definitive version is available at http://www.sciencedirect.com

Date Deposited: 10 Dec 2007 02:27
Last Modified: 18 Nov 2014 03:25
Item Statistics: View statistics for this item

Actions (login required)

Item Control Page Item Control Page
TOP