TY - JOUR
T1 - Trace element characteristics of partial melts produced by melting of metabasalts at high pressures
T2 - Constraints on the formation condition of adakitic melts
AU - Xiong, Xiaolin
AU - Adam, J.
AU - Green, T. H.
AU - Niu, Hecai
AU - Wu, Jinhua
AU - Cai, Zhiyong
PY - 2006/9
Y1 - 2006/9
N2 - Experiments were conducted on a natural basalt (with 5 wt.% added H2O) at 1.0-2.5 GPa and 900-1100°C. Experimental products include partial melts (quenched glasses) + residual mineral assemblages of amphibolite or eclogite. Electron microprobe and LAM-ICP-MS were used to determine major and trace element compositions of these quenched melts, respectively. Major element compositions of all the melts are tonalitic-trondhjemitic, similar to adakite. Their trace element characteristics are controlled by coexisting residual minerals. Signatures of adakite such as high Sr/Y, low HREE and negative Nb-Ta anomaly, etc. are present only in the melts coexisting with residual assemblages containing rutile and garnet (rutile-bearing eclogite or rutile-bearing amphibole-eclogite). Garnet leads to HREE depletion in melts, whereas rutile controls Nb and Ta partitioning during the partial melting and causes negative Nb-Ta anomaly in melts. Therefore, in addition to garnet, rutile is also a necessary residual phase during the generation of adakite or TTG magmas to account for the negative Nb-Ta anomaly of the magmas. The depth for the generation of adakite/TTG magmas via melting of metabasalt must be more than about 50 km based on the approximate 1.5 GPa minimum-pressure for rutile stability in the partial melting field of hydrous basalt.
AB - Experiments were conducted on a natural basalt (with 5 wt.% added H2O) at 1.0-2.5 GPa and 900-1100°C. Experimental products include partial melts (quenched glasses) + residual mineral assemblages of amphibolite or eclogite. Electron microprobe and LAM-ICP-MS were used to determine major and trace element compositions of these quenched melts, respectively. Major element compositions of all the melts are tonalitic-trondhjemitic, similar to adakite. Their trace element characteristics are controlled by coexisting residual minerals. Signatures of adakite such as high Sr/Y, low HREE and negative Nb-Ta anomaly, etc. are present only in the melts coexisting with residual assemblages containing rutile and garnet (rutile-bearing eclogite or rutile-bearing amphibole-eclogite). Garnet leads to HREE depletion in melts, whereas rutile controls Nb and Ta partitioning during the partial melting and causes negative Nb-Ta anomaly in melts. Therefore, in addition to garnet, rutile is also a necessary residual phase during the generation of adakite or TTG magmas to account for the negative Nb-Ta anomaly of the magmas. The depth for the generation of adakite/TTG magmas via melting of metabasalt must be more than about 50 km based on the approximate 1.5 GPa minimum-pressure for rutile stability in the partial melting field of hydrous basalt.
UR - http://www.scopus.com/inward/record.url?scp=33750983349&partnerID=8YFLogxK
U2 - 10.1007/s11430-006-0915-2
DO - 10.1007/s11430-006-0915-2
M3 - Article
AN - SCOPUS:33750983349
SN - 1006-9313
VL - 49
SP - 915
EP - 925
JO - Science in China, Series D: Earth Sciences
JF - Science in China, Series D: Earth Sciences
IS - 9
ER -