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John Malpas
University of Hong Kong
118Publications
32H-index
4,207Citations
Publications 119
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#1Peng-Fei Zhang (HKU: University of Hong Kong)H-Index: 4
#2Mei-Fu Zhou (HKU: University of Hong Kong)H-Index: 71
Last.Yongsheng He (China University of Geosciences)H-Index: 19
view all 6 authors...
Abstract Combined Fe isotopic and olivine fabric analyses have been conducted on the nodular chromitites from the Luobusa ophiolite, Tibet, to study the physico-chemical effects of plastic flow in modifying chromitites and their associated mantle peridotites below spreading centers. The Luobusa nodular chromitites are generally composed of fresh dunitic matrices and well-aligned chromite nodules. Olivine grains in both the dunitic matrices and chromite nodules underwent pressure solution, and th...
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#1Peng-Fei Zhang (HKU: University of Hong Kong)H-Index: 4
#2Mei-Fu Zhou (HKU: University of Hong Kong)H-Index: 71
Last.Paul T. Robinson (HKU: University of Hong Kong)H-Index: 14
view all 4 authors...
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#1Peng-Fei Zhang (HKU: University of Hong Kong)H-Index: 4
#2Mei-Fu Zhou (HKU: University of Hong Kong)H-Index: 71
Last.Xiaoping Xia (CAS: Chinese Academy of Sciences)H-Index: 34
view all 7 authors...
Abstract The Li-O isotopes of olivine and pyroxene from the mantle sequence of the Luobusa ophiolite, a fragment of Neo-Tethyan forearc lithosphere in Tibet, reveal a series of magmatic processes and geochemical evolution in a nascent mantle wedge during subduction initiation. Olivine grains from the ophiolitic mantle sequence display δ 18 O values similar to those of normal mantle (+5.18 ± 0.2‰), but have large δ 7 Li variations, ∼+4‰ to +13‰ in harzburgites and ∼+1‰ to +11‰ in high-Cr chromiti...
3 CitationsSource
#1Jian-Feng Gao (HKU: University of Hong Kong)H-Index: 30
#2Mei-Fu Zhou (HKU: University of Hong Kong)H-Index: 71
Last.John Malpas (HKU: University of Hong Kong)H-Index: 32
view all 6 authors...
The Tengchong volcanic field east of the Burma arc in SW China comprises numerous Quaternary volcanoes. The volcanic rocks can be grouped into four units, numbered 1–4 from oldest to youngest. Units 1, 3 and 4 are composed of trachybasalt, basaltic trachyandesite and trachyandesite, respectively, whereas Unit 2 consists of hornblende dacite. Primary minerals in the dacite include plagioclase, clinopyroxene, amphibole and magnetite, all set in a glassy groundmass. Some of the dacites are moderate...
22 CitationsSource
#1George S.-K. Ma (AS: Academia Sinica)H-Index: 5
#2Kuo-Lung Wang (AS: Academia Sinica)H-Index: 23
Last.Queenie H S Chan (HKU: University of Hong Kong)H-Index: 1
view all 9 authors...
Spongy minerals, especially clinopyroxenes, and fine-grained, often glass-bearing mineral assemblages , commonly referred to as melt pockets, occur in many mantle xenolith suites worldwide, but their origins remain far from being clearly understood. We describe a suite of spongy clinopyroxene- and melt pockets-bearing peridotite xenoliths from the Plio-Quaternary volcanic field in the Al Ghab Depression, a pull-apart basin of the Dead Sea Fault System in northwestern Syria. The melt pockets comp...
3 CitationsSource
#1Mei-Fu Zhou (HKU: University of Hong Kong)H-Index: 71
#2Paul T. Robinson (HKU: University of Hong Kong)H-Index: 14
Last.John Malpas (HKU: University of Hong Kong)H-Index: 32
view all 7 authors...
Abstract Podiform chromitites in the mantle sections of ophiolites belong to either high-Cr (metallurgical) or high-Al (refractory) varieties. Their highly variable compositions are reflected by different Cr#s [100Cr / (Cr + Al)] and Cr2O3 and Al2O3 contents of the chromite, falling in the boninitic and MORB fields, respectively. Parental magmas of high-Cr chromitites have higher Sc, Mn, Co and Ni, and lower Ti, V, Zn and Ga concentrations than MORB melts; their trace-element patterns are simila...
121 CitationsSource
#1Wei Wang (HKU: University of Hong Kong)H-Index: 42
#2Mei-Fu Zhou (HKU: University of Hong Kong)H-Index: 71
Last.John Malpas (HKU: University of Hong Kong)H-Index: 32
view all 5 authors...
Abstract Precambrian sedimentary sequences in the eastern Jiangnan Orogen, South China, include the Neoproterozoic Shuangqiaoshan and Xikou Groups and the overlying Nanhua Sequence. U–Pb ages of detrital zircons provide tight constraints on the deposition of the Shuangqiaoshan and Xikou Groups at 831–815 Ma and 833–817 Ma, respectively. Rocks from the lower parts of these strata contain dominantly Neoproterozoic detritus with a pronounced age peak at 830–850 Ma, interpreted to be derived from a ...
92 CitationsSource
#1George S.-K. Ma (AS: Academia Sinica)H-Index: 5
#2John Malpas (HKU: University of Hong Kong)H-Index: 32
Last.Costas Xenophontos (HKU: University of Hong Kong)H-Index: 13
view all 6 authors...
Early–Middle Miocene intraplate basalts from the Aleppo Plateau, NW Syria have been analysed for their platinum-group elements (PGEs). They contain extremely low PGE abundances, comparable with most alkali basalts, such as those from Hawaii, and mid-ocean ridge basalts. The low abundances, together with high Pd/Ir, Pt/Ir, Ni/Ir, Cu/Pd, Y/Pt and Cu/Zr are consistent with sulphide fractionation, which likely occurred during partial melting and melt extraction within the mantle. Some of the basalts...
5 CitationsSource
#1George S.-K. MaH-Index: 5
#2John MalpasH-Index: 32
Last.Costas XenophontosH-Index: 13
view all 6 authors...
abstract Article history:Received 21 December 2011Received in revised form 1 November 2012Accepted 2 November 2012Available online 12 November 2012Editor: L. ReisbergKeywords: 40 Ar/ 39 Ar geochronologyRe–Os isotopeMetasomatic veinIntraplate volcanismAmphiboleCrustal contamination Thesourceofintraplatebasaltshaslongbeenacontroversialtopic,particularlyincontinentalsettingswheream-biguity increasesbecause both crustal contamination andcrystalfractionation may mask important source char-acteristics...
2 Citations
#1George S.-K. Ma (AS: Academia Sinica)H-Index: 5
#2John Malpas (HKU: University of Hong Kong)H-Index: 32
Last.Costas Xenophontos (HKU: University of Hong Kong)H-Index: 13
view all 7 authors...
Abstract The source of intraplate basalts has long been a controversial topic, particularly in continental settings where ambiguity increases because both crustal contamination and crystal fractionation may mask important source characteristics. We present geochemical data to constrain the source and the chemical evolution of the continental intraplate magmas from the Aleppo Plateau and vicinity, NW Syria. New 40Ar/39Ar ages, coupled with published 40Ar/39Ar and K–Ar ages, reveal two discrete Mi...
19 CitationsSource
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