Zircons from two samples of the Sukeng pluton in the southwest Fujian Province, China, were analyzed by LA-ICP-MS with the aim of determining the timing of formation. The zircons from the two samples yield similar U-Pb ages of 100.47 ± 0.42 and 102.46 ± 0.69 Ma, indicating that the Sufeng pluton is contemporaneous with the Sifang and Luoboling plutons, all of which are also related to Cu-Au-Pb-Zn-Mo mineralization within the study area. All three plutons have geochemical features of I-type granites, are high-to mid-K calc-alkaline metaluminous rocks, and have average molar Al 2 O 3 / (CaO+Na 2 O+K 2 O) values of 0.95, initial 87 Sr/ 86 Sr ratios of 0.70465-0.70841, Nd(t) values at 101 Ma from -1.72 to -7.26, and two-stage Nd model ages (T 2DM ) from 1.16 to 1.60 Ga.Zircons within these plutons have Hf(t) values at 101 Ma from -3.5 to 6.25 and T 2DM ages from 0.74 to 1.46 Ga, suggesting these I-type granites formed from magmas generated by partial melting of Mesoproterozoic to Neoproterozoic continental crust that mixed with mantle-derived magmas. The magmatism was associated with thickening of the lower crust caused by collisions between microcontinents in the Cathaysian Block, which were driven by Early Cretaceous subduction of the Pacific Plate.

Southeast China is characterized by widespread Mesozoic igneous rocks, which have drawn a great deal of attention in recent decades because of their tectonic significance and related large‐scale mineralization. Among these igneous rocks, The Tangquan pluton in Southwest Fujian Province is the only adakitic pluton that has been discovered within the Cathaysian Block. It is mainly composed of a central unit of granodiorite with peripheral granodioritic porphyries. Two medium‐grained granodiorite samples have zircon U‐Pb ages of 162.2 ± 2.0 Ma and 163.0 ± 1.4 Ma, indicating intrusion in Middle Jurassic times. Adakite‐like geochemical features of the pluton include high Sr/Y (46.7) and (La/Yb)N (25.5) values, and low Y (12.2 ppm) and Yb (1.04 ppm) abundances. All samples have low εNd(t) values (average −9.49) and high initial 87Sr/86Sr ratios (average 0.708242). These results suggest that the adakitic rocks were generated by partial melting in thickened crust. The Tangquan pluton probably formed during the extrusion collision of microcontinents within the Cathaysian Block related to subduction of the Pacific Plate, which caused crustal thickening and partial melting of Neoproterozoic crust with arc‐like magmatic characteristics. Because the extrusion collision occurred between microcontinents in an intraplate (Cathaysian Block) setting, the effects of the extrusion collision were not as strongly felt as those involved in the Jiangshan‐Shaoxing Fault along which numerous adakitic rocks were emplaced with related porphyry‐type copper deposits. Copyright © 2016 John Wiley & Sons, Ltd.

The Honggong pluton is the largest ferroan alkalic (A-type) granite intrusion emplaced along the Jiangshan–Shaoxing fault zone in southwestern Zhejiang Province, and has important implications for understanding the Late Mesozoic tectonic evolution of SE China. U–Pb ages of 138.7 ± 0.8, 134.2 ± 1.1, 128.5 ± 1.5 and 126.1 ± 0.9 Ma were obtained from zircon by laser ablation–inductively coupled plasma–mass spectrometry, indicating that the Honggong pluton formed in the Early Cretaceous. The Honggong pluton has a clear ferroan alkalic (A-type) granite geochemical signature with, for example, high total alkali contents and FeOt/(FeOt + MgO) values. The Sr–Nd–Hf isotopic compositions suggest that there was juvenile material in the magma source. Geochemical evidence indicates that the pluton was derived through extensive fractionation of melts that contained both asthenospheric mantle and Mesoproterozoic crustal components. These rare granites in southern China were emplaced during five episodes at 235–225, 190, 165–155, 100–90 and 140–120 Ma. The age of the Honggong pluton suggests that localized extension in southwestern Zhejiang Province began as early as ~138 Ma and continued to 126 Ma. This Early Cretaceous extensional event was triggered by localized rollback of the subducting Pacific Plate.

No abstract

No abstract