U-Pb zircon ages and petrogeochemistry and tectonic implications of gabbro and granite in southwest Lahad Datu area of Sabah, Malaysia

• Published in: Acta oceanologica Sinica 2024-02, Vol.43 (2), p.94-110
• Main Authors: Zhao, Zhigang, Tang, Wu, Liu, Shixiang, Tang, Huafeng, Wang, Pujun, Tian, Zhiwen
• Format: Article
• Language: English
• Subjects: Age; Aluminum oxide; Basements; Chondrites; Climatology; Cretaceous; Diagenesis; Earth and Environmental Science; Earth mantle; Earth Sciences; Ecology; Engineering Fluid Dynamics; Environmental Chemistry; Fault lines; Gabbro; Geochemistry; Geochronometry; Granite; Hafnium; Igneous rocks; Island arcs; Isotopes; Lava; Lead; Magma; Marine & Freshwater Sciences; Oceanic crust; Oceanography; Oceans; Paleoceanography; Radiometric dating; Rare earth elements; Silica; Silicon dioxide; Tectonics; Titanium dioxide; Trace elements; Triassic; Zircon; Zirconium
• ISSN: 0253-505X; 1869-1099
• DOI: 10.1007/s13131-023-2218-2

The southwest Lahad Datu felsic rocks were previously thought to have formed in the late Triassic as part of the microcontinental crystalline basement. Based on U-Pb ages, geochemistry, and the Hf isotopes of zircon from the southeastern Sabah gabbro and granite, in this study, the tectonic properties of the Sabah area during the Triassic were investigated. The weighted average U-Pb zircon ages of the gabbro and granite samples were determined to be (230.9 ± 2.5)Ma and (207.1 ± 3.3)Ma, respectively. The granite had SiO 2 contents of 66.54%–79.47%, low TiO 2 contents of 0.08%−0.3%, Al 2 O 3 contents of 10.97%–16.22%, Na 2 O contents of 5.91%–6.39%, and low K 2 O contents of 0.15%–0.65%. The chondrite-normalized rare earth element (REE) patterns exhibit light REE enrichment, with right-sloping curves. The primitive mantle-normalized trace element spider diagrams exhibit Th, U, La, Sr, and Zr enrichment and Nb, Ta, P and Ti depletions, i.e., the geochemical characteristics of typical island arc igneous rocks. The tectonic discriminant diagram indicates that the granite is a volcanic arc granite. The Hf isotopic analysis of gabbro zircon revealed that the zircons have ε Hf ( t ) values of 12.08–16.24 (mean of 14.32) and two-stage model ages ( t DM2 ) of 223–491 Ma (mean of 347 Ma). This indicates that the diagenetic magma of the gabbro was mainly derived from melting of newly formed crustal materials. The ophiolite in southeast Sabah has existed since the early Late Triassic. The crystalline basement granite in southeastern Sabah was emplaced lasted from late Triassic to early Cretaceous. Based on previous studies and global plate reconstruction models, it is speculated that the southeastern Sabah granite may have been formed in an island arc setting, i.e., where the oceanic crust of the Paleo-Tethys Ocean collided with the oceanic crust of the Panthalassa Ocean.