Geochemistry, Zircon U–Pb Geochronology, and Lu–Hf Isotopes of the Chishan Alkaline Complex, Western Shandong, China

Abstract

Mass alkaline magmatic activities in Western Shandong during the late Mesozoic controlled the mineralization processes of gold and rare earth element (REE) polymetallic deposits in the region. The Chishan alkaline complex is closely associated with the mineralization of the Chishan REE deposit, which, as the third largest light REE deposit in China following the Baiyenebo (Inner Mongolia) and Mianning (Sichuan) deposits, is considered a typical example of alkaline rock mineralization throughout the North China Craton. To determine how the Chishan alkaline complex and REE deposit interact with each other, a systematic study was conducted on the petrology, rock geochemistry, zircon U–Pb geochronology, Lu–Hf isotopes of the quartz syenite, and alkali granite contained in the Chishan alkaline complex. The results reveal that the deposits feature similar geochemical characteristics typical of an alkaline rock series—both are rich in alkali, high in potassium, metaluminous, and poor in Ti, Fe, Mg, and Mn. In terms of REEs, the deposits are strongly rich in light REEs but poor in heavy REEs, with weak negative Eu anomalies. In terms of trace elements, they are rich in large ion lithophile elements Ba, Sr, and Rb but poor in high field-strength elements Nb, Ta, and Hf. Zircon LA-ICP-MS U–Pb dating indicated that the quartz syenite and alkali granite formed in Early Cretaceous at 125.8 ± 1.2 Ma and 127.3 ± 1.0 Ma, respectively; their εHf(t) values are −22.67 to −13.19, with depleted model ages (TDM) ranging from 1296 Ma to 1675 Ma and crustal model ages (TDMC) of 2036–2617 Ma. The Chishan alkaline complex originated from partial of the EM I-type (enriched mantle I) lithospheric mantle with assimilation of ancient crustal materials. The complex is of the same origin as the REE deposit, and developed in an extensional setting that resulted from plate subduction and lithospheric thinning and upwelling in the eastern area of the North China Craton.

Tectonic Transformation and Metallogenesis of the Yanshan Movement during the Late Jurassic Period: Evidence from Geochemistry and Zircon U-Pb Geochronology of the Adamellites in Xingcheng, Western Liaoning, China

“…Frequency diagrams of compiled geochronological ages (Figure 14) show that the magmatic rocks formed by multistage magmatism during the Mesozoic, overlapping the ages of major metalliferous deposits. This spatiotemporal consistency indicates a possible relationship between the formation of gold, molybdenum deposits, and magmatism in the north of the NCC, the magmatism likely provides the thermodynamic condition and the source of metallogenic hydrothermal fluid for mineralization [21][22][23]91]. Combined with previous research results, it has been shown that the Mesozoic endogenetic metalliferous deposits formed in a compressive environment influenced by the subduction of the Paleo-Pacific plate similar to the magma events in the north of the NCC [80,83,92,93].…”

“…Also, the granitic magma related to mineralization is of high emplacement without eruption, so that the volatile and the metallogenic elements are well preserved to form the large-scale mineralization in the region. Thus, the fault clefts are always constructions of ore-conducting and ore-bearing structures and in a condition of formation of deposits or ore-bodies [22,23,77,90]. For example, the Wulong Gold Mine in Liaoning province was affected by the Yanshanian tectonic-magmatic.…”

“…Intense and frequent magmatic activities control the formation of the gold and metal metallogenesis [14,[17][18][19][20][21][22]. For example, the formation of the large Wulongshan gold deposits and the Meishan polymetallic deposits in Eastern Shandong were genetically related to the acidic magmas [21,[23][24][25], and some gold and REE deposits in Western Shandong were controlled by alkaline magmas [23,[25][26][27]. These ore-controlling magmas might originate from the upper mantle with complicated underplating and hybrid processes [23], and record the tectonic evolution of the Yanshan Movement.…”

“…For example, the formation of the large Wulongshan gold deposits and the Meishan polymetallic deposits in Eastern Shandong were genetically related to the acidic magmas [21,[23][24][25], and some gold and REE deposits in Western Shandong were controlled by alkaline magmas [23,[25][26][27]. These ore-controlling magmas might originate from the upper mantle with complicated underplating and hybrid processes [23], and record the tectonic evolution of the Yanshan Movement. In this study, the Xudapu adamellites in Xingcheng area, western Liaoning were investigated in terms of the geochemistry characters, chronology, and petrogenesis to provide constraints on the tectonic transformation of the Jurassic tectonic movements, and to facilitate the understanding of the deep geodynamic mechanism of the Yanshan Movement and Yanshannian magmatism, as well as their relationships with metallogenesis.…”

Editorial for Special Issue “Polymetallic Metallogenic System”

“…In addition, garnet Sm-Nd dating is conducted on the Hongshan skarn deposits to further constrain the timing of skarn formation in Zu et al [27]. The emplacement ages and geochemical and isotopic signatures of ore-related intrusions are also proved to be genetically linked with the formation of mineral deposits [28][29][30][31][32][33][34].…”