Systematic variations in magmatic sulphide chemistry from mid-ocean ridges, back-arc basins and island arcs

Journal article
(Original article)


Publication Details

Author(s): Keith M, Haase K, Klemd R, Schwarz-Schampera U, Franke H
Journal: Chemical Geology
Publisher: Elsevier B.V.
Publication year: 2017
Volume: 451
Pages range: 67-77
ISSN: 0009-2541
Language: English


Abstract


Immiscible sulphide liquids preserved as magmatic sulphide globules are hosted in igneous rocks of highly variable composition formed during magmatic processes at different tectonic settings. Here we report on compositional in situ data of magmatic sulphides from mid-ocean ridge, back-arc and island arc magmatic systems. Iron-Ni-rich monosulphide solid solutions (mss) that mainly consist of pyrrhotite and pentlandite are the dominant phases in magmatic sulphide globules. In subduction-related magmas mss are most abundant in relatively evolved melts and characterised by low Ni and high Fe contents, as well as low Ni/Cu ratios (< 1). In contrast, mss from mid-ocean ridges and back-arcs without subduction input occur in mafic rocks and have high Ni/Cu ratios (> 1). Thus, mss chemistry varies systematically in lavas from the different tectonic settings in terms of their Fe-Ni distribution and Ni/Cu ratio. The observed mineralogical and chemical variations between mss from the different settings reflect early S saturation accompanied by olivine fractionation along mid-ocean ridges compared to later stage S saturation in arc systems associated with Fe-Ti oxide fractionation. These systematics are probably related to the relatively oxidised character of subduction zone magmas opposed to more reduced mid-ocean ridge melts. Large Ni/Cu variations in mss from the same locality and in individual samples suggest that S saturation is a multistage or continuous process leading to inclusions of magmatic sulphides that represent different fractionation stages in the ascending magma.



FAU Authors / FAU Editors

Haase, Karsten Prof. Dr.
Lehrstuhl für Endogene Geodynamik
Keith, Manuel
Lehrstuhl für Endogene Geodynamik
Klemd, Reiner Prof. Dr.
Professur für Geochemie und Lagerstättenkunde


External institutions
Bundesanstalt für Geowissenschaften und Rohstoffe (BGR)


How to cite

APA:
Keith, M., Haase, K., Klemd, R., Schwarz-Schampera, U., & Franke, H. (2017). Systematic variations in magmatic sulphide chemistry from mid-ocean ridges, back-arc basins and island arcs. Chemical Geology, 451, 67-77. https://dx.doi.org/10.1016/j.chemgeo.2016.12.028

MLA:
Keith, Manuel, et al. "Systematic variations in magmatic sulphide chemistry from mid-ocean ridges, back-arc basins and island arcs." Chemical Geology 451 (2017): 67-77.

BibTeX: 

Last updated on 2018-17-10 at 05:40