https://repository.kopri.re.kr/handle/201206/5144 Fri, 10 Apr 2026 02:36:05 GMT 2026-04-10T02:36:05Z https://repository.kopri.re.kr/handle/201206/6233 Title: Mantle dyanmics beneath East Asia constrained by Sr, Nd, Pb and Hf isotopic systematics of ultramafic xenoliths and their host basalts from Hannuoba, North China Authors: Mukasa SB; Choi, Sung Hi; Andronikov AV; Xian XH; Zhou X-H Abstract: We have determined the Sr, Nd, Pb and Hf isotopic compositions of clinopyroxene separated from mantle-derived ultramafic xenoliths (six spinel peridotites, one composite Cr-diopside pyroxenite, and one discrete Al-augite pyroxenite) hosted by Cenozoic alkali basalts at Hannuoba, North China, in order to understand the nature of the mantle source for this intraplate volcanism, and the evolutional history of the mantle lithosphere beneath North China Block, a crustal fragment of the Sino-Korean Craton. Measured Sr, Nd, Pb and Hf isotopic compositions in the clinopyroxene grains separated from spinel peridotite and Cr-diopside pyroxenite (87Sr/86Sr = 0.70265 to 0.70485;206Pb/204Pb = 17.75 to 19.15;？Nd = 0 to +11;？Hf = +10 to +38) display mixing hyperbolas between DMM and EM2 on the Sr？Pb and Nd？Pb isotope correlation diagrams. This is distinctly different relative to the host basalt data which show a mixture of DMM and EM1 components on the diagrams. We interpret this to reflect infiltration by metasomatic agents, possibly silicate melts having an EM2-like isotopic signature that enriched a precursor time-integrated depleted mantle. An Al-augite pyroxenite also hosted by these basalts is characterized by highly enriched Sr, Nd, and Hf isotopic compositions (87Sr/86Sr = 0.70733;？Nd = -16;？Hf = -18) with only moderately radiogenic Pb that has a 206Pb/204Pb value of 18.23. All of these data plot outside (1) the fields for oceanic basalts, and (2) the mixing arrays defined by peridotites/Cr-diopside pyroxenite with their metasomatic agents, and by the host basalt on the isotopic correlation diagrams. These observations suggest that (1) Al-augite pyroxenite is not cogenetic with the Cr-diopside pyroxenite, (2) parental melts of the pyroxenites are not likely to be the source for the metasomatism, and (3) the thermo/mechanically reactivated pyroxenite and/or spinel peridotite, is not likely to be the source for host basalt mag Tue, 01 Jan 2008 00:00:00 GMT https://repository.kopri.re.kr/handle/201206/6233 2008-01-01T00:00:00Z https://repository.kopri.re.kr/handle/201206/7749 Title: Lu-Hf systematics of the ultra-high temperature Napier metamorphic complex in Antarctica Authors: Choi, Sung Hi; N.M. Kelly; Y. Osanai; S.L. Harley; A.V. Andronikov; Samuel B. Mukasa Abstract: The Napier Complex of the East Antarctic Craton comprises some of the oldest rocks on earth (~3.8 billion years old), overprinted by an ultra-high temperature (UHT) metamorphic event near the Archean-Proterozoic boundary. Garnet, orthopyroxene, sapphirine, osumilite, rutile and a whole rock representing a fully equilibrated assemblage from this UHT granulite belt have yielded a Lu-Hf isochron age of 2,403 +/- 43 Ma, the first ever determined on a UHT mineral assemblage. Preservation of the UHT mineral assemblage in the rock analyzed, without any significant retrogression, suggests rapid cooling with closure likely to have occurred for the Lu-Hf system at post-peak UHT conditions near a temperature of ~800C. This mineral-whole rock isochron yields an initial 176Hf/177Hf ratio corresponding to an eHf value of -14 +/- 1, acquired during UHT metamorphism. Such a low value demonstrates that overall UHT granulites evolved in a low Lu/Hf environment, probably formed when the rocks were first extracted from a highly depleted mantle. Zircon eHf values we have measured "see through" the UHT metamorphism and show that the source materials for the magmas that formed the Napier Complex were extremely depleted (> +5.6 eHf at 3.85 Ga) relative to the chondritic uniform reservoir (CHUR). These results also suggest significant depletion of the early Archean mantle, in agreement with the early differentiation of the earth that the latest core formation models require. Mon, 01 Jan 2007 00:00:00 GMT https://repository.kopri.re.kr/handle/201206/7749 2007-01-01T00:00:00Z https://repository.kopri.re.kr/handle/201206/7748 Title: Lu-Hf systematics of the ultra-high temperature Napier metamorphic complex in Antarctica Authors: Y. Osanai; N.M. Kelly; Choi, Sung Hi; Samuel B. Mukasa; A.V. Andronikov; S.L. Harley Abstract: The Napier Complex of the East Antarctic Craton comprises some of the oldest rocks on earth (~3.8 billion years old), overprinted by an ultra-high temperature (UHT) metamorphic event near the Archean-Proterozoic boundary. Garnet, orthopyroxene, sapphirine, osumilite, rutile and a whole rock representing a fully equilibrated assemblage from this UHT granulite belt have yielded a Lu-Hf isochron age of 2,403 +/- 43 Ma, the first ever determined on a UHT mineral assemblage. Preservation of the UHT mineral assemblage in the rock analyzed, without any significant retrogression, suggests rapid cooling with closure likely to have occurred for the Lu-Hf system at post-peak UHT conditions near a temperature of ~800C. This mineral-whole rock isochron yields an initial 176Hf/177Hf ratio corresponding to an eHf value of -14 +/- 1, acquired during UHT metamorphism. Such a low value demonstrates that overall UHT granulites evolved in a low Lu/Hf environment, probably formed when the rocks were first extracted from a highly depleted mantle. Zircon eHf values we have measured "see through" the UHT metamorphism and show that the source materials for the magmas that formed the Napier Complex were extremely depleted (> +5.6 eHf at 3.85 Ga) relative to the chondritic uniform reservoir (CHUR). These results also suggest significant depletion of the early Archean mantle, in agreement with the early differentiation of the earth that the latest core formation models require. Mon, 01 Jan 2007 00:00:00 GMT https://repository.kopri.re.kr/handle/201206/7748 2007-01-01T00:00:00Z https://repository.kopri.re.kr/handle/201206/7739 Title: Lu-Hf systematics of the ultra-high temperature Napier Complex, East Antarctica Authors: N.M. Kelly; S.L. Harley; Choi, Sung Hi; Samuel B. Mukasa; Y. Osanai; A.V. Andronikov Abstract: The Napier Complex comprises some of the oldest rocks on earth (~3.8 billion years old), overprinted by an ultra-high temperature (UHT) metamorphic event near the Archean Proterozoic boundary. Garnet, orthopyroxene, sapphirine, osumilite, rutile and a whole rock representing a fully equilibrated assemblage from this UHT granulite belt have yielded a Lu Hf isochron age of 2,403 +/- 43 Ma. Preservation of the UHT mineral assemblage in the rock analyzed suggests rapid cooling with closure likely to have occurred for the Lu-Hf system at post-peak UHT conditions near a temperature of ~800C. Zircon eHf values we have measured "see through" the UHT metamorphism and show that the source materials for the magmas that formed the Napier Complex were extremely depleted (> +5.6 eHf at 3.85 Ga) relative to the chondritic uniform reservoir (CHUR). These results also suggest significant depletion of the early Archean mantle, in agreement with the early differentiation of the earth that the latest core formation models require. Mon, 01 Jan 2007 00:00:00 GMT https://repository.kopri.re.kr/handle/201206/7739 2007-01-01T00:00:00Z