SHRIMP zircon U-Pb dating of the Neoproterozoic Maoping （茅坪） series （Sandouping （三斗坪） rock suite） granites exposed in the southern part of the Huangling （黄陵） anticline shows that the formation time of S...SHRIMP zircon U-Pb dating of the Neoproterozoic Maoping （茅坪） series （Sandouping （三斗坪） rock suite） granites exposed in the southern part of the Huangling （黄陵） anticline shows that the formation time of Sandouping biotite-hornblende tonalite intrusion, Jinpansi （金盘寺） hornblende-biotite tonalite intrusion, and Longtanping （龙潭坪） monzogranite are 863±9, 842±10, and 844±10 Ma, respectively. Their geochemical features include A/CNK=0.98-1.06, from metaluminous to weakly peraluminous, δ=1.37-1.53, Sm/Nd=0.17-0.24, and RbN/YbN=1.1-3.62. These indicate that the granite rocks are supersaturated SiO2 calc-alkaline granitoids. The characteristic of Sr-Nd isotopic composition is that the values of εNd（t） and εsr（t） are -12.4 to -11.0 and 20.2-32.2, respectively. It also suggests that the material source of the granite rocks mainly originated from the crust, and they formed in a volcanic arc tectonic environment. These facts suggest that the occurrence of Neoproterozoic granitoids in the southern part of the Huangling anticline should be related to an arc environment along an active continental margin caused by southward subduction of oceanic crust beneath the northern Yangtze craton, and the formation age is not later than 863 Ma.展开更多
基金supported by the China Geological Survey Project (Nos. 1212010710715 and 1212011085340)
文摘SHRIMP zircon U-Pb dating of the Neoproterozoic Maoping （茅坪） series （Sandouping （三斗坪） rock suite） granites exposed in the southern part of the Huangling （黄陵） anticline shows that the formation time of Sandouping biotite-hornblende tonalite intrusion, Jinpansi （金盘寺） hornblende-biotite tonalite intrusion, and Longtanping （龙潭坪） monzogranite are 863±9, 842±10, and 844±10 Ma, respectively. Their geochemical features include A/CNK=0.98-1.06, from metaluminous to weakly peraluminous, δ=1.37-1.53, Sm/Nd=0.17-0.24, and RbN/YbN=1.1-3.62. These indicate that the granite rocks are supersaturated SiO2 calc-alkaline granitoids. The characteristic of Sr-Nd isotopic composition is that the values of εNd（t） and εsr（t） are -12.4 to -11.0 and 20.2-32.2, respectively. It also suggests that the material source of the granite rocks mainly originated from the crust, and they formed in a volcanic arc tectonic environment. These facts suggest that the occurrence of Neoproterozoic granitoids in the southern part of the Huangling anticline should be related to an arc environment along an active continental margin caused by southward subduction of oceanic crust beneath the northern Yangtze craton, and the formation age is not later than 863 Ma.
