Origin and geological significance of the 1.81 Ga hyalophane-rich pegmatite veins from the high-pressure granulite terrain in the Central Zone of North China Craton  

作　　者：QU Min GUO JingHui LAI Yong PENG Peng LIU Fu 

机构地区：[1]State Key Laboratory of Lithospheric Evolution,Institute of Geology and Geophysics,Chinese Academy of Sciences,Beijing 100029,China [2]The Key Laboratory of Orogenic Belts and Crustal Evolution,Ministry of Education,Peking University,Beijing 100871,China

出　　处：《Science China Earth Sciences》2012年第2期193-203,共11页中国科学（地球科学英文版）

基　　金：supported by National Natural Science Foundation of China (Grant Nos. 40730315 and 41023009);State Key Laboratory of Lithospheric Evolution

摘　　要：Hyalophane-rich pegmatites are identified from the Manjinggou high-pressure granulite terrain in the Central Zone of North China Craton. Based on field investigation, mineral assemblage and mineral geochemistry, two types of pegmatites can be defined, i.e., hyalophane pegmatite and hyalophane-rich pegmatite. The hyalophane pegmatite is composed of pure hyalophane with 18.7 mol%-19.4 mol% celsian, whereas the hyalophane-rich pegmatite consists of clinopyroxene + titanite + epidote + hyalophane with 11.9 mol%-12.5 mol% celsian. Hyalophane-rich pegmatite has typical magmatic zircons with oscillatory zoning and high Th/U ratios, implying that this type of pegmatite crystallized from special melt similar to magma. SIMS (Cameca 1280) zircon U-Pb dating shows that the crystallization age of the hyalophane-rich pegmatite is 1812±5 Ma, younger than the regional metamorphic age (peak of ca. 1.85 Ga). Zircon δ18O (8.0 ‰-9.3 ‰) and ?Hf (-7.0 to-2.7) values measured by SIMS suggest that the high-pressure granulite terrain was the source of these veins. Therefore, the hyalophane-rich pegmatite veins were likely to be generated by melting of the high-pressure granulite terrain during post collisional uplift. A quick tectonic uplifting process with a velocity of 0.4 to 0.6 mm/a has been estimated for the high-pressure granulite terrane from the Central Zone of North China Craton.Hyalophane-rich pegmatites are identified from the Manjinggou high-pressure granulite terrain in the Central Zone of North China Craton. Based on field investigation, mineral assemblage and mineral geochemistry, two types of pegmatites can be defined, i.e., hyalophane pegmatite and hyalophane-rich pegmatite. The hyalophane pegmatite is composed of pure hyalophane with 18.7 mol%–19.4 mol% celsian, whereas the hyalophane-rich pegmatite consists of clinopyroxene ＋ titanite ＋ epidote ＋ hyalophane with 11.9 mol%–12.5 mol% celsian. Hyalophane-rich pegmatite has typical magmatic zircons with oscillatory zoning and high Th/U ratios, implying that this type of pegmatite crystallized from special melt similar to magma. SIMS （Cameca 1280） zircon U-Pb dating shows that the crystallization age of the hyalophane-rich pegmatite is 1812±5 Ma, younger than the regional metamorphic age （peak of ca. 1.85 Ga）. Zircon δ18O （8.0 ‰–9.3 ‰） and ？Hf （–7.0 to–2.7） values measured by SIMS suggest that the high-pressure granulite terrain was the source of these veins. Therefore, the hyalophane-rich pegmatite veins were likely to be generated by melting of the high-pressure granulite terrain during post collisional uplift. A quick tectonic uplifting process with a velocity of 0.4 to 0.6 mm/a has been estimated for the high-pressure granulite terrane from the Central Zone of North China Craton.

关 键 词：hyalophane PEGMATITE zircon Hf-O isotope high-pressure granulite PALEOPROTEROZOIC North China Craton 

分 类 号：P588.346[天文地球—岩石学] P597[天文地球—地质学]