The Luoguhe intrusion, located in MoheCounty, Heilongjiang Province, is mainly composed of mon-zogranite, quartz diorite and granodiorite, with minor dio-rite, tonalite, quartz monzodiorite, quartz monzonite, syeno-gr...The Luoguhe intrusion, located in MoheCounty, Heilongjiang Province, is mainly composed of mon-zogranite, quartz diorite and granodiorite, with minor dio-rite, tonalite, quartz monzodiorite, quartz monzonite, syeno-granite and alkali-feldspar granite. The intrusion can bedivided into two lithological units, i.e. quartz diorite andmonzogranite units, with affinities to high-K calc-alkalineseries. The quartz diorite unit (SiO2: 54.79%―58.30%Na2O/CaO: 0.79―1.53 and Shand index: 0.77―0.82) belongsto 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. Theintrusion is characterized by high REE abundance (∑REE =180.2―344.3 μg/g), medium-strong negative Eu anomalies(δ Eu = 0.33―0.82), weak REE fractionation [(La/Yb)N =4.12―10.45], enrichments in Rb, Th, U, K, La, Ce, Nd, HfZr and Sm, but strong depletions of Ba, Nb, Ta, Sr, P and TiThese characteristics of major, REE and trace elements in-dicate that the intrusion was formed in a transitional tectonicsetting from compressional to extensional regime, which canbe classified as post-collisional granitoids. SHRIMP U-Pbzircon analyses yield ages of 517±9 and 504±8 Ma for thequartz diorite and monzogranite units, respectively. The dis-covery of Early Paleozoic post-collisional granites in thenorthern margin of the Erguna massif indicates that thenorthern branch of Paleo-Asian Ocean between Siberianplate and Erguna massif was closed in the Early Paleozoicand the Salair orogeny ended ca. 500 Ma ago.展开更多
U-Pb zircon dating on two foliated garnet-bearing granite samples in the western Dabie ultra-high-pressure (UHP) metamorphic unit yields concordant ages of (234±4) Ma and (227±5) Ma, respectively. These ages...U-Pb zircon dating on two foliated garnet-bearing granite samples in the western Dabie ultra-high-pressure (UHP) metamorphic unit yields concordant ages of (234±4) Ma and (227±5) Ma, respectively. These ages, following the UHP peak metamorphism, represent the magma emplacement ages for the foliated garnet-bearing granites. This, for the first time, shows that there are the Triassic granites in the Dabie Mountains. The foliated garnet-bearing granites resemble A-type granite in geochemical characteristics, indicating that they were formed in exten-sional geodynamic setting. The magma formation reflects a reheating event in the Dabie orogenic belt and it enhances the transfer of tectonic regime from collision into extension and promotes the rapid exhumation into lower crust for the UHP metamorphic rocks.展开更多
基金This work was supported by the National Resources Compensation from the Ministry of Land Mineral Resources of China(Grant No.2001170191).
文摘The Luoguhe intrusion, located in MoheCounty, Heilongjiang Province, is mainly composed of mon-zogranite, quartz diorite and granodiorite, with minor dio-rite, tonalite, quartz monzodiorite, quartz monzonite, syeno-granite and alkali-feldspar granite. The intrusion can bedivided into two lithological units, i.e. quartz diorite andmonzogranite units, with affinities to high-K calc-alkalineseries. The quartz diorite unit (SiO2: 54.79%―58.30%Na2O/CaO: 0.79―1.53 and Shand index: 0.77―0.82) belongsto 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. Theintrusion is characterized by high REE abundance (∑REE =180.2―344.3 μg/g), medium-strong negative Eu anomalies(δ Eu = 0.33―0.82), weak REE fractionation [(La/Yb)N =4.12―10.45], enrichments in Rb, Th, U, K, La, Ce, Nd, HfZr and Sm, but strong depletions of Ba, Nb, Ta, Sr, P and TiThese characteristics of major, REE and trace elements in-dicate that the intrusion was formed in a transitional tectonicsetting from compressional to extensional regime, which canbe classified as post-collisional granitoids. SHRIMP U-Pbzircon analyses yield ages of 517±9 and 504±8 Ma for thequartz diorite and monzogranite units, respectively. The dis-covery of Early Paleozoic post-collisional granites in thenorthern margin of the Erguna massif indicates that thenorthern branch of Paleo-Asian Ocean between Siberianplate and Erguna massif was closed in the Early Paleozoicand the Salair orogeny ended ca. 500 Ma ago.
基金This work was supported by the National Natural Science Foundation of China (Grant Nos. 49794043 and 40073005) and the Ministry of Science and Technology of China (Grant No. G1999075506).
文摘U-Pb zircon dating on two foliated garnet-bearing granite samples in the western Dabie ultra-high-pressure (UHP) metamorphic unit yields concordant ages of (234±4) Ma and (227±5) Ma, respectively. These ages, following the UHP peak metamorphism, represent the magma emplacement ages for the foliated garnet-bearing granites. This, for the first time, shows that there are the Triassic granites in the Dabie Mountains. The foliated garnet-bearing granites resemble A-type granite in geochemical characteristics, indicating that they were formed in exten-sional geodynamic setting. The magma formation reflects a reheating event in the Dabie orogenic belt and it enhances the transfer of tectonic regime from collision into extension and promotes the rapid exhumation into lower crust for the UHP metamorphic rocks.
