Zh. Wang et al., Effect of melt-rock interaction on geochemistry in the Kudi ophiolite (western Kunlun Mountains, northwestern China): implication for ophiolite origin, EARTH PLAN, 191(1-2), 2001, pp. 33-48
Major, trace and rare earth elements (REE), and platinum group elements (PG
E) geochemistry have been studied for the Kudi ophiolite in the northwester
n part of the western Kunlun Mountains, northwestern China, in order to det
ermine the relationship between the mantle peridotites and mafic lavas and
the origin of the ophiolite. The ophiolite consists of harzburgites, dunite
s, cumulate dunites, pyroxenites and gabbros, diabase dykes, and pillow and
massive lavas. The mantle peridotites are rich in Mg and Ni and poor in Al
and Ca. The pyroxene is low in Al and Ti, and the spinel is high in Cr# (C
r#>0.6), similar to those from ophiolites in supra-subduction zone environm
ents. The cumulate rocks are mainly pyroxenites and gabbros and are Nb- and
Ti-depleted. The Kudi mafic lavas with marked No and Ti depletion can be d
ivided into two groups as shown by their trace, rare earth element and isot
opic characteristics: group I basalts with more pronounced are signature, a
nd diabase dykes and group 2 basalts, respectively. The mantle peridotites,
cumulates, diabase dykes and group 2 basalts probably constitute an upper
mantle and crustal section of a back-arc basin in a SSZ environment. The en
richment of incompatible trace elements (such as Rb, Ba, Th), light REE and
Pd in the mantle peridotites indicates that an interaction between the man
tle peridotites and the parental magma of group I basalts has probably occu
rred. This interaction obviously affected the trace and rare earth elements
, and PGE geochemical characteristics of the mantle peridotites. The parent
al magma contained a distinctive Pd-rich melt and may be spatially related
to arc magmatism. (C) 2001 Elsevier Science B.V. All rights reserved.