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Discovery of the Early Paleozoic post-collisional granites in northern margin of the Erguna massif and its geological significance
作者姓名:WU  Guang  SUN  Fengyue  ZHAO  Caisheng  LI  Zhitong  ZHAO  Ailin  PANG  Qingbang  LI  Guangyuan
作者单位:[1]College of Earth Sciences, Jilin University, Changchun 130026, China [2]Shenyang Institute of Geology and Mineral Resources, Shenyang 110032, China [3]Institute of Mineral Resources, Chinese Academy of Geological Sciences, Beijing 100037, China
摘    要:The Luoguhe intrusion, located in Mohe County, Heilongjiang Province, is mainly composed of monzogranite, quartz diorite and granodiorite, with minor diorite, tonalite, quartz monzodiorite, quartz monzonite, syenogranite and alkali-feldspar granite. The intrusion can be divided into two iithological units, i.e. quartz diorite and monzogranite units, with affinities to high-K caic-alkaline series. The quartz diorite unit (SiO2: 54.79%-58.30%, Na2O/CaO: 0.79-1.53 and Shand index: 0.77-0.82) belongs to metaluminous rocks. And the monzogranite unit (SiO2: 65.29%-66.45%, Na2O/CaO: 1.73-3.43 and Shand index 〈1.05) can be considered as weakly peraluminous rocks. The intrusion is characterized by high REE abundance (∑REE = 180.2-344.3μg/g), medium-strong negative Eu anomalies (δEu = 0.33-0.82), weak REE fractionation (La/Yb)N = 4.12-10.45], enrichments in Rb, Th, U, K, La, Ce, Nd, Hf, Zr and Sm, but strong depletions of Ba, Nb, Ta, Sr, P and Ti. These characteristics of major, REE and trace elements indicate that the intrusion was formed in a transitional tectonic setting from compressionai to extensional regime, which can be classified as post-collisional granitoids. SHRIMP U-Pb zircon analyses yield ages of 517±9 and 504±8 Ma for the quartz diorite and monzogranite units, respectively. The discovery of Early Paleozoic post-collisionai granites in the northern margin of the Erguna massif indicates that the northern branch of Paleo-Asian Ocean between Siberian plate and Erguna massif was closed in the Early Paleozoic and the Salair orogeny ended ca. 500 Ma ago.

关 键 词:花岗岩  U-Pb测年  早古生代  地球化学  地质学
收稿时间:2005-01-27
修稿时间:2005-01-272005-07-07

Discovery of the Early Paleozoic post-collisional granites in northern margin of the Erguna massif and its geological significance
WU Guang SUN Fengyue ZHAO Caisheng LI Zhitong ZHAO Ailin PANG Qingbang LI Guangyuan.Discovery of the Early Paleozoic post-collisional granites in northern margin of the Erguna massif and its geological significance[J].Chinese Science Bulletin,2005,50(23):2733-2743.
Authors:Wu Guana  Sun Fengyue  Zhao Caisheng  Li Zhitong  Zhao Ailin  Pang Qingbang  Li Guangyuan
Institution:(1) College of Earth Sciences, Jilin University, 130026 Changchun, China;(2) Shenyang Institute of Geology and Mineral Resources, 110032 Shenyang, China;(3) Institute of Mineral Resources, Chinese Academy of Geological Sciences, 100037 Beijing, China
Abstract:The Luoguhe intrusion, located in Mohe County, Heilongjiang Province, is mainly composed of monzogranite, quartz diorite and granodiorite, with minor diorite, tonalite, quartz monzodiorite, quartz monzonite, syenogranite and alkali-feldspar granite. The intrusion can be divided into two lithological units, i.e. quartz diorite and monzogranite units, with affinities to high-K calc-alkaline series. The quartz diorite unit (SiO2: 54.79%–58.30%, Na2O/CaO: 0.79–1.53 and Shand index: 0.77–0.82) belongs to metaluminous rocks. And the monzogranite unit (SiO2: 65.29%–66.45%, Na2O/CaO: 1.73–3.43 and Shand index < 1.05) can be considered as weakly peraluminous rocks. The intrusion is characterized by high REE abundance (ΣREE = 180.2-344.3 μg/g), medium-strong negative Eu anomalies (δEu = 0.33-0.82), weak REE fractionation (La/Yb)N = 4.12-10.45], enrichments in Rb, Th, U, K, La, Ce, Nd, Hf, Zr and Sm, but strong depletions of Ba, Nb, Ta, Sr, P and Ti. These characteristics of major, REE and trace elements indicate that the intrusion was formed in a transitional tectonic setting from compressional to extensional regime, which can be classified as post-collisional granitoids. SHRIMP U-Pb zircon analyses yield ages of 517±9 and 504±8 Ma for the quartz diorite and monzogranite units, respectively. The discovery of Early Paleozoic post-collisional granites in the northern margin of the Erguna massif indicates that the northern branch of Paleo-Asian Ocean between Siberian plate and Erguna massif was closed in the Early Paleozoic and the Salair orogeny ended ca. 500 Ma ago.
Keywords:post-collisional granite  SHRIMP U-Pb dating  Early Paleozoic  geochemistry  Erguna massif
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