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| 1 | Corundum formation by metasomatic reactions in Archean metapelite,SW Greenland:Exploration vectors for ruby deposits within high-grade greenstone belts显示文摘Corundum(ruby-sapphire) is known to have formed in situ within Archean metamorphic rocks at several localities in the North Atlantic Craton of Greenland. Here we present two case studies for such occurrences:(1) Maniitsoq region(Kangerdluarssuk), where kyanite paragneiss hosts ruby corundum, and(2)Nuuk region(Stor?), where sillimanite gneiss hosts ruby corundum. At both occurrences, ultramafic rocks(amphibole-peridotite) are in direct contact with the ruby-bearing zones, which have been transformed to mica schist by metasomatic reactions. The bulk-rock geochemistry of the ruby-bearing rocks is consistent with significant depletion of SiO_2 in combination with addition of Al_2O_3, MgO, K_2O,Th and Sr relative to an assumed aluminous precursor metapelite. Phase equilibria modelling supports ruby genesis from the breakdown of sillimanite and kyanite at elevated temperatures due to the removal of SiO_2. The juxtaposition of relatively silica-and aluminum-rich metasedimentary rocks with low silica ultramafic rocks established a chemical potential gradient that leached/mobilized SiO_2 allowing corundum to stabilize in the former rocks. Furthermore, addition of Al_2O_3 via a metasomatic reaction is required, because Al/Ti is fractionated between the aluminous precursor metapelites and the resulting corundum-bearing mica schist. We propose that Al was mobilized either by complexation with hydroxide at alkaline conditions, or that Al was transported as K-Al-Si-O polymers at deep crustal levels.The three main exploration vectors for corundum within Archean greenstone belts are:(1) amphiboliteto granulite-facies metamorphic conditions,(2) the juxtaposition of ultramafic rocks and aluminous metapelite, and(3) mica-rich reactions zones at their interface. | Chris Yakymchuk Kristoffer Szilas | 2018 | Geoscience Frontiers2018，9，3： | 2 |
| 2 | The reactivity of Tanzanian Minjingu phosphate rock can be assessed from the chemical and mineralogical composition显示文摘 | C. Szilas C. Bender Koch M.M. Msolla O.K. Borggaard | 2008 | Geoderma2008，，： | 1 |
| 3 | Sorption of glyphosate and phosphate by variable-charge tropical soils from Tanzania 显示文摘 | Gimsing A L Szilas C Borggaard O K | 2007 | Geoderma2007，138，12： | 1 |
| 4 | Efficient Inhibition of Muscle and Liver Glycogen Phosphorylases by a New Glucopyranosylidene-Spirothiohydantoin显示文摘 | OSZ E SOMS'K L SZILA'GYI L | 1999 | Bioorg Med Chem Lett1999，9，： | 1 |
| 5 | The reactivity of Tanzanian Minjingu phosphate rock can be assessed from the chemical and mineralogical composition 显示文摘 | SZILAS C BENDER KOCH C MSOLLA M M | 2008 | Geoderma2008，147，34： | 1 |
| 6 | Sorption of glyphosate and phosphate by variable-charge tropical soils from Tanzania 显示文摘 | Gimsing A L Szilas C Borggaard O K | 2007 | Geoderma2007，138，： | 1 |
| 7 | Syntheses of Novel Glycosylidene-Spiroheterocycles Related to Hydantocidin 显示文摘 | OSZ E SZILA'GYI L SOMS'K L | 1999 | Tetrahedron1999，55，： | 1 |
| 8 | Potential iron and phosphate mobilization during flooding of soil material 显示文摘 | Szilas C P Borggard O K Hansen H C B | 1998 | Water Air and Soil Pollution1998，106，： | 1 |
| 9 | Potential iron and phosphate mobilization during flooding of soil material显示文摘 | Szilas CP Borgaard OK Hansen HCB Rauer J | 1998 | Water Air and Pollution1998，106，1： | 1 |
| 10 | Potential iron and phosphate mobilization during flooding of soil material显示文摘 | SZILAS C P BORGGAARD O K HANSEN H C B | 1998 | Water Air Soil Pollut1998，106，12： | 1 |
| 11 | Sorption of glyphosate and phosphate by variable - charge tropical soils from Tanzania 显示文摘 | Gimsing A L Szilas C Borggaard O K | 2007 | Geoderma2007，138，1： | 1 |
| 12 | The reactivity of Tanzanian Minjingu phosphate rock can be assessed from the chemical and mineralogical composition显示文摘 | Szilas C Bender Koch C Msolla M M | 2008 | Geoderma2008，147，34： | 1 |
| 13 | Deserpentinization and high-pressure(eclogite-facies) metamorphic features in the Eoarchean ultramafic body from Isua,Greenland显示文摘Discontinuous chains of ultramafic rock bodies form part of the 3800–3700 Ma Isua Supracrustal Belt(ISB),hosted in the Itsaq Gneiss Complex of southwestern Greenland.These bodies are among the world’s oldest outcrops of ultramafic rocks and hence an invaluable geologic record.Ultramafic rocks from Lens B in the northwestern limb of ISB show characteristics of several stages of serpentinization and deserpentinization forming prograde and retrograde mineral assemblages.Ti-rich humite-group minerals such as titanian chondrodite(Ti-Chn)and titanian clinohumite(Ti-Chu)often occur as accessory phases in the metamorphosed ultramafic rocks.The Ti-rich humite minerals are associated with metamorphic olivine.The host olivine is highly forsteritic(Fo96-98)with variable Mn O and Ni O contents.The concentrations of the rare-earth elements(REE)and high-field strength elements(HFSE)of the metamorphic olivine are higher than typical mantle olivine.The textural and chemical characteristics of the olivine indicate metamorphic origin as a result of deserpentinization of a serpentinized ultramafic protolith rather than primary assemblage reflecting mantle residues from high-degrees of partial melting.The close association of olivine,antigorite and intergrown Ti-Chn and Ti-Chu suggests pressure condition between$1.3–2.6 GPa within the antigorite stability field(<700°C).The overall petrological and geochemical features of Lens B ultramafic body within the Eoarchean ISB indicate that these are allochthonous ultramafic rocks that recorded serpentine dehydration at relatively lower temperature and reached eclogite facies condition during their complex metamorphic history similar to exhumed UHP ultramafic rocks in modern subduction zone channels. | Juan Miguel Guotana Tomoaki Morishita Ikuya Nishio Akihiro Tamura Tomoyuki Mizukami Kenichiro Tani Yumiko Harigane Kristoffer Szilas D.Graham Pearson | 2022 | Geoscience Frontiers2022，13，1： | 0 |
| 14 | Highly refractory Archaean peridotite cumulates:Petrology and geochemistry of the Seqi Ultramafic Complex,SW Greenland显示文摘This paper investigates the petrogenesis of the Seqi Ultramafic Complex, which covers a total area of approximately 0.5 km^2. The ultramafic rocks are hosted by tonalitic orthogneiss of the ca. 3000 Ma Akia terrane with crosscutting granitoid sheets providing an absolute minimum age of 2978 ± 8 Ma for the Seqi Ultramafic Complex. The Seqi rocks represent a broad range of olivine-dominated plutonic rocks with varying modal amounts of chromite, orthopyroxene and amphibole, i.e. various types of dunite(s.s.),peridotite(s.l.), as well as chromitite. The Seqi Ultramafic Complex is characterised primarily by refractory dunite, with highly forsteritic olivine with core compositions having Mg# ranging from about 91 to 93. The overall high modal contents, as well as the specific compositions, of chromite rule out that these rocks represent a fragment of Earth's mantle. The occurrence of stratiform chromitite bands in peridotite, thin chromite layers in dunite and poikilitic orthopyroxene in peridotite instead supports the interpretation that the Seqi Ultramafic Complex represents the remnant of a fragmented layered complex or a magma conduit, which was subsequently broken up and entrained during the formation of the regional continental crust.Integrating all of the characteristics of the Seqi Ultramafic Complex points to formation of these highly refractory peridotites from an extremely magnesian(Mg# ~ 80), near-anhydrous magma, as olivinedominated cumulates with high modal contents of chromite. It is noted that the Seqi cumulates were derived from a mantle source by extreme degrees of partial melting(>40%). This mantle source could potentially represent the precursor for the sub-continental lithospheric mantle(SCLM) in this region,which has previously been shown to be ultra-depleted. The Seqi Ultramafic Complex, as well as similar peridotite bodies in the Fiskefjord region, may thus constitute the earliest cumulates that formed during the large-scale melting event(s), which resulted in the ultra-depleted cratonic keel under the North Atlantic Craton. Hence, a better understanding of such Archaean ultramafic complexes may provide constraints on the geodynamic setting of Earth's first continents and the corresponding SCLM. | Kristoffer Szilas Vincent van Hinsberg Iain McDonald Tomas Naeraa Hugh Rollinson Jacob Adetunji Dennis Bird | 2018 | Geoscience Frontiers2018，9，3： | 0 |
| 15 | Zircon within chromitite requires revision of the tectonic history of the Eoarchean Itsaq Gneiss complex,Greenland显示文摘The Ujaragssuit Nunat layered(UNL)unit in the Itsaq Gneiss Complex,west Greenland,has been consid-ered to contain one of the oldest chromitites on Earth based on~ca.4.1 Ga Hadean whole rock Pt-Os model ages and ca.3.81 Ga zircon U-Pb age of the surrounding orthogneiss.This study obtained zircon from the chromitite within this unit as well as granitoid sheets that intruded into the UNL unit.In-situ U-Pb-Hf-O isotope measurements were made on the zircons.Zircons from both the chromitite and the intrusive granitoids show concordant U-Pb ages of ca.2.97-2.95 Ga.In contrast,Hf and 0 isotopic anal-yses indicate that zircons in the chromitites have a different origin from those in the intrusive granitoids.Zircons from granitoids yielded Th/U ratios higher than 0.2,initial Hf isotope ratios of 0.2805-0.2807(i.e,initial:Hf value of-11 to-5),andδ^(18)O values of mostly 6.0‰-7.0‰,which are typical for felsic igneous rocks in Archean continental crust.The least altered zircons from a chromitite exhibited initial Hf isotope ratios of 0.28078-0.28084(i.e.,initial:Hf value of-1.1 to-0.4),close the chondritic value at ca.3.0 Ga and the depleted mantle at ca.3.2 Ga.These zircons also haveδ^(18)O values of 4.2‰6.1‰which correspond to typical mantle values.The other chromitite zircons yielded Th/U ratios lower than 0.1,and Hf and 0 isotopic compositions ranging between the least altered zircons and the intrusive granitoid zir-cons.These results indicate that the zircons in the chromitites crystallized before or during the 2.97-2.95 Ga granitoid intrusion and most of the zircons were altered by subsequent metasomatism.Furthermore,the present results suggest that zircons in the chromitites originally had depleted Hf iso-topic compositions at ca.3.2-3.0 Ga.This can be explained by two different models of the evolution of the UNL unit.One is that if the UNL unit was formed at>3.81 Ga as previously thought,with the zircons in the chromitites subsequently being precipitated by ca.3.2-2.95 Ga during metamorphism or metaso-matism.The other model is that the UNL unit itself was actually formed at ca.3.2-3.0 Ga,with zircon in the chromitite representing the crystallisation age of the unit,which was then tectonically incorporated into the ca.3.81 Ga orthogneiss prior to the 2.97-2.95 Ga granitoid intrusion event.In either case,our zircon analyses reveal significant evolutionary history prior to depleted mantle Hf model ages of 3.2-2.95 Ga.Revision of the geotectonic evolution of the UNL unit and the Itsaq Gneiss Complex is therefore required. | Hikaru Sawada Tomoaki Morishita Adrien Vezinet Richard Stern Kenichiro Tani Ikuya Nishio Kanta Takahashi D.Graham Pearson Kristoffer Szilas | 2023 | Geoscience Frontiers2023，14，6： | 0 |
| 16 | 太古宙绿岩带中铬铁矿床研究现状与展望显示文摘太古宙绿岩带中铬铁矿床不仅具有重要经济价值,而且是研究地球早期物质组成和地幔演化的重要对象。太古宙铬铁矿床形成时代久远,普遍经历了后期复杂的变质、变形和流体改造等一系列地质作用。相较于显生宙豆荚状铬铁矿和元古宙层状铬铁矿,对太古宙绿岩带内产出铬铁矿的研究还较为薄弱,尤其对铬铁矿体形成的地质背景和岩浆作用缺乏深入系统的研究。本文综述了格陵兰、印度、澳大利亚西部、加拿大以及津巴布韦等典型太古宙绿岩带中铬铁矿床的主要地质特征和研究现状,讨论了相关科学问题和研究展望。绿岩带中铬铁矿床主要产在古太古代-新太古代(3.3~2.7Ga)克拉通内的超基性岩石单元中,矿体常与蛇纹石化纯橄岩伴生。铬铁矿体产状复杂,既有层状和似层状,也有透镜状和不规则状,因此不能简单归于层状铬铁矿或豆荚状铬铁矿。铬铁矿岩以块状为主,其铬铁矿Cr#相对较高(>60),属高铬型,Mg#中等偏高(21~93)且与Cr#呈负相关关系。研究认为,绿岩带中铬铁矿的成矿母岩浆来自深部亏损含水地幔分异所形成的科马提质岩浆,且受到了地壳物质混染。在开放的岩浆房内,含矿原始母岩浆与不断补给的科马提质岩浆相混合,并随着岩浆的重力分异和对流分层等作用形成堆晶状铬铁矿体。 | 王嘉玮 蔡鹏捷 SZILAS Kristoffer 连东洋 杨经绥 | 2023 | 岩石学报2023，39，12： | 0 |
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