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Article: Garnet-bearing tonalitic porphyry from East Kunlun, Northeast Tibetan Plateau: Implications for adakite and magmas from the MASH Zone

TitleGarnet-bearing tonalitic porphyry from East Kunlun, Northeast Tibetan Plateau: Implications for adakite and magmas from the MASH Zone
Authors
KeywordsAdakite
Garnet
Kunlun
MASH Zone
Tibetan Plateau
Issue Date2009
PublisherSpringer Verlag. The Journal's web site is located at http://link.springer.de/link/service/journals/00531/index.htm
Citation
International Journal Of Earth Sciences, 2009, v. 98 n. 6, p. 1489-1510 How to Cite?
AbstractA garnet-bearing tonalitic porphyry from the Achiq Kol area, northeast Tibetan Plateau has been dated by SHRIMP U-Pb zircon techniques and gives a Late Triassic age of 213 ± 3 Ma. The porphyry contains phenocrysts of Ca-rich, Mn-poor garnet (CaO > 5 wt%; MnO < wt%), Al-rich hornblende (Al 2O 3 ∼ 15.9 wt%), plagioclase and quartz, and pressure estimates for hornblende enclosing the garnet phenocrysts yield values of 8 - 10 kbar, indicating a minimum pressure for the garnet. The rock has SiO 2 of 60 - 63 wt%, low MgO (<2.0 wt%), K 2O (<1.3 wt%), but high Al 2O 3 (>17 wt%) contents, and is metaluminous to slightly peraluminous (ACNK = 0.89 - 1.05). The rock samples are enriched in LILE and LREE but depleted in Nb and Ti, showing typical features of subduction-related magmas. The relatively high Sr/Y (∼38) ratios and low HREE (Yb < 0.8 ppm) contents suggest that garnet is a residual phase, while suppressed crystallization of plagioclase and lack of negative Eu anomalies indicate a high water fugacity in the magma. Nd - Sr isotope compositions of the rock (εNd T = -1.38 to -2.33; 87Sr/ 86Sr i = 0.7065 - 0.7067) suggest that both mantle- and crust-derived materials were involved in the petrogenesis, which is consistent with the reverse compositional zoning of plagioclase, interpreted to indicate magma mixing. Both garnet phenocrysts and their ilmenite inclusions contain low MgO contents which, in combination with the oxygen isotope composition of garnet separates (+6.23‰), suggests that these minerals formed in a lower crust-derived felsic melt probably in the MASH zone. Although the rock samples are similar to adakitic rocks in many aspects, their moderate Sr contents (<260 ppm) and La/Yb ratios (mostly 16 - 21) are significantly lower than those of adakitic rocks. Because of high partition coefficients for Sr and LREE, fractionation of apatite at an early stage in the evolution of the magma may have effectively decreased both Sr and LREE in the residual melt. It is suggested that extensive crystallization of apatite as an early phase may prevent some arc magmas from evolving into adakitic rocks even under high water fugacity. © Springer-Verlag 2008.
Persistent Identifierhttp://hdl.handle.net/10722/58686
ISSN
2015 Impact Factor: 2.133
2015 SCImago Journal Rankings: 0.992
ISI Accession Number ID
Funding AgencyGrant Number
National Basic Research Program of China2007CB411308
NSFC40421303
40572043
40725009
Hong Kong RGCHKU 7040/04
Funding Information:

We thank Qian Mao, Yuguang Ma and Ms. Ying Liu for their help with the analytical work. The authors benefited from discussions with Drs Guochun Zhao, Hongfu Zhang, Nengsong Chen, Chunming Wu and Petra Bach. We also appreciate the constructive and encouraging comments of reviewers Ali Polat and Fu- yuan Wu, which helped us to improve and clarify the manuscript. This work was supported by research grants from the National Basic Research Program of China (973 Program) 2007CB411308, NSFC Projects 40421303, 40572043, 40725009 and Hong Kong RGC (HKU 7040/04).

References

 

DC FieldValueLanguage
dc.contributor.authorYuan, Cen_HK
dc.contributor.authorSun, Men_HK
dc.contributor.authorXiao, Wen_HK
dc.contributor.authorWilde, Sen_HK
dc.contributor.authorLi, Xen_HK
dc.contributor.authorLiu, Xen_HK
dc.contributor.authorLong, Xen_HK
dc.contributor.authorXia, Xen_HK
dc.contributor.authorYe, Ken_HK
dc.contributor.authorLi, Jen_HK
dc.date.accessioned2010-05-31T03:35:01Z-
dc.date.available2010-05-31T03:35:01Z-
dc.date.issued2009en_HK
dc.identifier.citationInternational Journal Of Earth Sciences, 2009, v. 98 n. 6, p. 1489-1510en_HK
dc.identifier.issn1437-3254en_HK
dc.identifier.urihttp://hdl.handle.net/10722/58686-
dc.description.abstractA garnet-bearing tonalitic porphyry from the Achiq Kol area, northeast Tibetan Plateau has been dated by SHRIMP U-Pb zircon techniques and gives a Late Triassic age of 213 ± 3 Ma. The porphyry contains phenocrysts of Ca-rich, Mn-poor garnet (CaO > 5 wt%; MnO < wt%), Al-rich hornblende (Al 2O 3 ∼ 15.9 wt%), plagioclase and quartz, and pressure estimates for hornblende enclosing the garnet phenocrysts yield values of 8 - 10 kbar, indicating a minimum pressure for the garnet. The rock has SiO 2 of 60 - 63 wt%, low MgO (<2.0 wt%), K 2O (<1.3 wt%), but high Al 2O 3 (>17 wt%) contents, and is metaluminous to slightly peraluminous (ACNK = 0.89 - 1.05). The rock samples are enriched in LILE and LREE but depleted in Nb and Ti, showing typical features of subduction-related magmas. The relatively high Sr/Y (∼38) ratios and low HREE (Yb < 0.8 ppm) contents suggest that garnet is a residual phase, while suppressed crystallization of plagioclase and lack of negative Eu anomalies indicate a high water fugacity in the magma. Nd - Sr isotope compositions of the rock (εNd T = -1.38 to -2.33; 87Sr/ 86Sr i = 0.7065 - 0.7067) suggest that both mantle- and crust-derived materials were involved in the petrogenesis, which is consistent with the reverse compositional zoning of plagioclase, interpreted to indicate magma mixing. Both garnet phenocrysts and their ilmenite inclusions contain low MgO contents which, in combination with the oxygen isotope composition of garnet separates (+6.23‰), suggests that these minerals formed in a lower crust-derived felsic melt probably in the MASH zone. Although the rock samples are similar to adakitic rocks in many aspects, their moderate Sr contents (<260 ppm) and La/Yb ratios (mostly 16 - 21) are significantly lower than those of adakitic rocks. Because of high partition coefficients for Sr and LREE, fractionation of apatite at an early stage in the evolution of the magma may have effectively decreased both Sr and LREE in the residual melt. It is suggested that extensive crystallization of apatite as an early phase may prevent some arc magmas from evolving into adakitic rocks even under high water fugacity. © Springer-Verlag 2008.en_HK
dc.languageengen_HK
dc.publisherSpringer Verlag. The Journal's web site is located at http://link.springer.de/link/service/journals/00531/index.htmen_HK
dc.relation.ispartofInternational Journal of Earth Sciencesen_HK
dc.rightsThe original publication is available at www.springerlink.com-
dc.subjectAdakiteen_HK
dc.subjectGarneten_HK
dc.subjectKunlunen_HK
dc.subjectMASH Zoneen_HK
dc.subjectTibetan Plateauen_HK
dc.titleGarnet-bearing tonalitic porphyry from East Kunlun, Northeast Tibetan Plateau: Implications for adakite and magmas from the MASH Zoneen_HK
dc.typeArticleen_HK
dc.identifier.openurlhttp://library.hku.hk:4550/resserv?sid=HKU:IR&issn=1437-3254&volume=98&issue=6&spage=1489&epage=1510&date=2009&atitle=Garnet-bearing+tonalitic+porphyry+from+East+Kunlun,+Northeast+Tibetan+Plateau:+implications+for+adakite+and+magmas+from+the+MASH+Zoneen_HK
dc.identifier.emailSun, M: minsun@hku.hken_HK
dc.identifier.emailXia, X: xpxia@hotmail.comen_HK
dc.identifier.authoritySun, M=rp00780en_HK
dc.identifier.authorityXia, X=rp00815en_HK
dc.description.naturelink_to_subscribed_fulltext-
dc.identifier.doi10.1007/s00531-008-0335-yen_HK
dc.identifier.scopuseid_2-s2.0-69849088903en_HK
dc.identifier.hkuros161223en_HK
dc.relation.referenceshttp://www.scopus.com/mlt/select.url?eid=2-s2.0-69849088903&selection=ref&src=s&origin=recordpageen_HK
dc.identifier.volume98en_HK
dc.identifier.issue6en_HK
dc.identifier.spage1489en_HK
dc.identifier.epage1510en_HK
dc.identifier.isiWOS:000269376400017-
dc.publisher.placeGermanyen_HK
dc.identifier.scopusauthoridYuan, C=35241599200en_HK
dc.identifier.scopusauthoridSun, M=25932315800en_HK
dc.identifier.scopusauthoridXiao, W=7202456615en_HK
dc.identifier.scopusauthoridWilde, S=35254758600en_HK
dc.identifier.scopusauthoridLi, X=7501704180en_HK
dc.identifier.scopusauthoridLiu, X=8890184100en_HK
dc.identifier.scopusauthoridLong, X=14012199100en_HK
dc.identifier.scopusauthoridXia, X=35241486400en_HK
dc.identifier.scopusauthoridYe, K=7102173832en_HK
dc.identifier.scopusauthoridLi, J=26643194200en_HK

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