Petrology and Geochemistry of Mantle Peridotite Xenoliths from SE China   总被引：11，自引：2，他引：9  

QI  Q. U.; TAYLOR  LAWRENCE A; ZHOU  XINMIN 《Journal of Petrology》1995,36(1):55-79

Geochemical data on Type I spinel peridotite and garnet peridotitexenoliths in Cenozoic basalts from SE China demonstrate thatthe lithospheric mantle under this region is heterogeneous.The depletion and enrichment shown by these peridotite xenolithsare not related to their locations as suggested earlier. Samplesfrom individual localities, at the continental margin or thecontinental interior, show large variational ranges from depletedharzburgite to fertile Iherzolite. The measured Nd and Sr isotopiccompositions of clinopyroxene separates range from _Nd 49 to160 and from ⁸⁷Sr/⁸⁶Sr 070256 to 070407, respectively. Thedepleted signatures of Sr and Nd isotopic compositions and major-elementcontents (low CaO and Al₂O₃ in most xenoliths require an olddepletion event, probably mid-Proterozftic, and the enrichmentof LREE in the depleted peridotites implies a young metasomaticevent shortly before Cenozoic magmatism. Major-element compositionsof the peridotite xenoliths are controlled largely by the degreeof partial melting, and the extra fertile peridotites (highCaO and Al₂O₃) are probably the products of interaction betweenperidotites and a basaltic component. The equilibrium P–Tconditions, determined from coexisting mineral phases, indicatethat these xenoliths equilibrated over a wide P–T range,from 770 to 1250 C and from 10 to 27 kbar. Calculated oxygenfugacities for most spinel peridotites range from near the FMQbuffer to 25 log units below. The late-stage metasomatism didnot change the redox state in the upper mantle. ^*Corraponding author  相似文献   

Genesis of Young Lithospheric Mantle in Southeastern China: an LAM-ICPMS Trace Element Study   总被引：29，自引：4，他引：25  

XU  XISHENG; OREILLY  SUZANNE Y.; GRIFFIN  W.L.; ZHOU  XINMIN 《Journal of Petrology》2000,41(1):111-148

Geological and geophysical evidence indicates that at least100 km of Archaean to Proterozoic lithospheric mantle has beenremoved from beneath large areas of eastern and southeasternChina during late Mesozoic to Cenozoic time. Mantle-derivedxenoliths in Tertiary basalts from several localities acrossthis region have been studied by X-ray fluorescence, electronmicroprobe and laser ablation microprobe–inductively coupledplasma-mass spectrometry to characterize this thinner lithosphere.Trace element patterns of clinopyroxenes in the peridotitesfrom southeastern China can be divided into four groups: fertilegarnet lherzolites, fertile spinel (± garnet) lherzolites,and depleted and enriched peridotites. The addition of Nb, Sr,light rare earth elements, but not of Ti and Zr, suggests ametasomatizing agent containing both H₂O and CO₂. This studyalso demonstrates that the negative Ti anomaly commonly observedin clinopyroxene from mantle peridotites cannot be balancedby the Ti in coexisting orthopyroxene, but can be explainedby small degrees of partial melting, using appropriate distributioncoefficients. Most of the peridotites from southeastern China,whether spinel or garnet facies, are highly fertile in termsof Al₂O₃ and CaO contents and mg-number; many resemble commonlyused primitive mantle compositions. Modelling of trace elementpatterns in clinopyroxene indicates that most spinel and garnetperidotites from the Nushan, Mingxi and Niutoushan localitiesexperienced less than 5%, and many less than 2%, partial melting.A few depleted spinel peridotites from Nushan, and all spinelperidotites from Mingxi, require 10–25% fractional partialmelting; almost all spinel peridotites from the Qilin localityshow evidence of higher degrees (6–25%) of fractionalpartial melting. At both Nushan and Mingxi, the more depletedcompositions occur in the upper part of the lithospheric mantle,which now is  相似文献