TY - JOUR
T1 - Trace-element partitioning between synthetic potassic-richterites and silicate melts, and contrasts with the partitioning behaviour of pargasites and kaersutites
AU - Tiepolo, Massimo
AU - Zanetti, Alberto
AU - Oberti, Roberta
AU - Brumm, Richard
AU - Foley, Stephen
AU - Vannucci, Riccardo
PY - 2003/3
Y1 - 2003/3
N2 - Solid/liquid partition coefficients for large ion lithophile elements (Ba, Rb, Sr), high field strength elements (Zr, Hf, Nb, Ta, Ti), rare earth elements (La-Yb), Pb, Th, U and selected transition elements (Sc, V) were determined by means of Secondary Ion Mass Spectrometry on potassic-richterites synthesised at upper mantle conditions (P = 1.4 GPa and T = 850-1020°C) from silica-rich lamproites. Most trace elements display an incompatible behaviour in potassic-richterites; only Sr, Ti, Sc and V show strong positive anomalies in the partitioning pattern. When S/LD for potassic-richterites are compared with those for calcic amphiboles (pargasites and kaersutites) several differences become evident. In general, S/LD are lower in potassic-richterites; also, different partitioning patterns are apparent for RE and LIL elements. These differences are discussed in terms of the distinct crystal-chemical behaviour of the involved amphibole end-members, with particular emphasis to the available charge-balance mechanisms and to the site dimensional constraints ruling incorporation of trace elements in the various sites. The distinct partitioning behaviours of trace elements in potassic-richterites and pargasites and kaersutites imply that melts produced from amphibole-bearing sources may differ markedly depending on the type of amphibole crystallised. Therefore, the new partitioning data are used to discuss the role of potassic-richterite in its principal modes of occurrence, namely in lamproites, in peralkaline ultramafic veins in the lithospheric mantle, and in the deeper parts of subduction zones.
AB - Solid/liquid partition coefficients for large ion lithophile elements (Ba, Rb, Sr), high field strength elements (Zr, Hf, Nb, Ta, Ti), rare earth elements (La-Yb), Pb, Th, U and selected transition elements (Sc, V) were determined by means of Secondary Ion Mass Spectrometry on potassic-richterites synthesised at upper mantle conditions (P = 1.4 GPa and T = 850-1020°C) from silica-rich lamproites. Most trace elements display an incompatible behaviour in potassic-richterites; only Sr, Ti, Sc and V show strong positive anomalies in the partitioning pattern. When S/LD for potassic-richterites are compared with those for calcic amphiboles (pargasites and kaersutites) several differences become evident. In general, S/LD are lower in potassic-richterites; also, different partitioning patterns are apparent for RE and LIL elements. These differences are discussed in terms of the distinct crystal-chemical behaviour of the involved amphibole end-members, with particular emphasis to the available charge-balance mechanisms and to the site dimensional constraints ruling incorporation of trace elements in the various sites. The distinct partitioning behaviours of trace elements in potassic-richterites and pargasites and kaersutites imply that melts produced from amphibole-bearing sources may differ markedly depending on the type of amphibole crystallised. Therefore, the new partitioning data are used to discuss the role of potassic-richterite in its principal modes of occurrence, namely in lamproites, in peralkaline ultramafic veins in the lithospheric mantle, and in the deeper parts of subduction zones.
KW - Alkaline rocks
KW - Amphibole
KW - Experimental petrology
KW - Partition coefficients
KW - Potassic-richterite
KW - Trace elements
UR - http://www.scopus.com/inward/record.url?scp=0037367061&partnerID=8YFLogxK
U2 - 10.1127/0935-1221/2003/0015-0329
DO - 10.1127/0935-1221/2003/0015-0329
M3 - Article
VL - 15
SP - 329
EP - 340
JO - European Journal of Mineralogy
JF - European Journal of Mineralogy
SN - 0935-1221
IS - 2
ER -