Zircon U–Pb geochronological, geochemical, and Sr–Nd isotope data for Early Cretaceous mafic dykes in the Tancheng–Lujiang Fault area of the Shandong Province, China: Constraints on the timing of magmatism and magma genesis. (February 2015)

• Record Type: Journal Article
• Authors: Liu, Shen; Feng, Caixia; Hu, Ruizhong; Zhai, Mingguo; Gao, Shan; Lai, Shaocong; Yan, Jun; Coulson, Ian M.; Zou, Haibo
• Is Part Of: Journal of Asian earth sciences. Volume 98(2015)
• Page Start: 247
• Page End: 260
• Publication Date: 2015-02
• Subjects: Age -- Origin -- Hybridization -- Tan–Lu Fault -- NCC -- Yangtze Craton; Earth sciences -- Asia -- Periodicals; Sciences de la terre -- Asie -- Périodiques; Earth sciences; Asia; Periodicals; 555.05
• DOI: 10.1016/j.jseaes.2014.11.001
• Languages: English
• ISSNs: 1367-9120

Abstract

Graphical abstract: Highlights: Late Mesozoic mafic dykes in the Tan–Lu Fault were dated between 130 and 125 Ma. The dykes were derived from enriched mantle source. The origin of the dykes is related to the foundered lower crust beneath the eastern NCC. Abstract: The timing and source of magmatism that formed Early Cretaceous dolerite dykes in the Tancheng–Lujiang (Tan–Lu) Fault area of the southeastern North China Craton was determined using geochronological, geochemical, and whole-rock Sr–Nd isotopic data. Laser ablation–inductively coupled plasma–mass (LA–ICP–MS) spectrometry U–Pb analysis of zircon yielded consistent ages of 129.6 ± 0.7, 126.8 ± 0.7, 125.5 ± 0.7, 124.9 ± 0.9, 126.4 ± 0.7, and 125.5 ± 0.7 Ma for six samples of the mafic dykes within the NCC. The K2 O + Na2 O concentrations (5.02–5.21 wt.%) of the dykes indicate they are alkaline and these dykes have K2 O concentrations (2.35–2.48 wt.%) that indicate they are shoshonitic. These dolerites are also characterized by high and wide ranging (La/Yb)N (14.5–36.0), have slightly negative Eu anomalies (δEu = 0.70–0.91) and positive Ba, U, K, and Pb anomalies, and are depleted in the high field strength elements (Nb, Ta, P, and Ti). In addition, these mafic dykes are characterized by high radiogenic Sr [( 87 Sr/ 86 Sr)i = 0.7099–0.7100] and negative ε Nd ( t ) values (−14.4 to −13.7). These data suggest that the magmas that formed the dykes were derived through the partial melting (12.0–15.0%) of an enriched region of the mantle that was hybridized during interaction with subducted sedimentary rocks from the Yangtze Craton. The parental magmas then fractionated olivine and Fe–Ti oxides during ascent and underwent negligible crustal contamination during magma emplacement. These mafic magmas were finally emplaced as dyke swarms associated with lithospheric extension.