Zircon UPb Geochronology of IntermediateFelsic Dykes from the Jiangjunhe Area in Northern Shiquan, South Qinling Mountains and Its Geological Significance
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    Abstract:

    Numerous intermediatefelsic dykes are present in the northern part of Shiquan County in the South Qinling region. Most of the dykes have a structural contact relation with strata. But the relationship between formation age and gold mineralization in this area has been debated. In this study, a total of 13 rock samples were collected from several intermediatefelsic dykes in the northern part of Shiquan County. Field observation and indoor identification suggest that these dykes belong to diorite. The major elements analysis shows that diorite has a SiO2 content of 53.19%~68.48%, with A/CNK value of 0.67~1.28 and Rittman index (σ) of 1.4~2.93. The REE compositions indicate that intermediatefelsic dykes have a lower content of total REE (ΣREE=(44.54~253.23)×106) and are characterized by significant light REE enrichments relative to heavy REE (HREE/LREE=6.15~14.87, with (La/Yb)N=5.97~38.67) and weak negative Eu anomaly(δEu=0.68~0.88). Trace element analysis shows an obvious enrichment of lithophile elements (such as Ba, K, Sr), and depletion of high field strength elements (such as HREE, Ti, P, Th), indicating that these dykes were the products of lower crust remelting induced by the oceanic lithosphere subduction. Single zircon UPb dating age (771.9 ± 3.4 Ma) of diorite dykes is synchronous to that of the complex in southern Hanzhong and the Neopaleozoic magmatic activity at Fenghuangshan Mts north of Ankang, indicating a tectonic setting of regional extension breakup. Field geological mapping indicates that the Neoproterozoic dikes in the Jiangjunhe area has no direct genetic relation with the formation of gold deposits.

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DUAN Shaoshuai, JIAO Jiangang, LUO Dezhi, HUANG Xifeng, WANG Shuo, CHEN Binglong.2017. Zircon UPb Geochronology of IntermediateFelsic Dykes from the Jiangjunhe Area in Northern Shiquan, South Qinling Mountains and Its Geological Significance[J]. Acta Geologica Sinica,91(4):748-761

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  • Online: April 25,2017
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