Petrology and geochemistry of the Archean Huangling greenstone belt in the Yangtze Craton, South China

• Published in: Precambrian research Vol. 364; p. 106340
• Main Author: Wei, Junqi
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 15.09.2021
• Subjects: Amphibolite; Archean Huangling greenstone belt; Komatiite; Mantle plume; Tholeiitic basalt; Yangtze Craton; Tholeiitic basalt; Amphibolite; Archean Huangling greenstone belt; Komatiite; Yangtze Craton; Mantle plume
• ISSN: 0301-9268; 1872-7433
• DOI: 10.1016/j.precamres.2021.106340

•Archean Huangling greenstone belt is preserved as amphibolites in Yangtze Craton.•The protoliths of amphibolites include komatiite, komatiitic and tholeiitic basalt.•The tholeiitic basalts originated from a mantle plume head.•The komatiites originated from a mantle plume tail.•These ultramafic–mafic lavas erupted in a continental rift. The Archean Huangling greenstone belt (HGB) is preserved as amphibolites in the Huangling granite–greenstone terrane, Yangtze Craton. Geologically and geochemically, the amphibolites are metavolcanic rocks and can be subdivided into amphibole schist, massive amphibolite and banded amphibolite, with komatiite, komatiitic basalt and tholeiitic basalt protoliths, respectively. The komatiites have high MgO (20–30%), Cr, Co and Ni contents; low Rb, Sr, Ba and ΣREE contents; and slight LREE depletion and HREE enrichment, characterizing them as the Al-undepleted type according to the criteria (CaO/Al2O3)adj ˃ 20, (Al 2O3/TiO2)adj and (Gd/Yb)PM < 1. The komatiitic basalts and tholeiitic basalts have lower MgO (5–16%), Cr, Co and Ni contents; higher Rb, Sr, Ba and ΣREE contents; and slight LREE enrichment and HREE depletion. The geochemical plots (Zr/Y vs. Nb/Y, Nb/Yb vs. Th/Yb, La/Ta vs. La/Sm and Y vs. Zr/Y), negative Nb anomalies, wide ƐNd values (−8.0 to +6.2), negative zircon ƐHf values (−11.59 to −3.98), and old TNd (DM) (3.9–2.9 Ga) and zircon THf (DM) ages (3.9–3.3 Ga) of the amphibolites reflect a mantle source with slight crustal contamination and show that the komatiitic basalts and tholeiitic basalts are more closely related to each other than to the komatiites. The tholeiitic basalts originated from moderate-degree melting of a mantle plume head, the komatiitic basalts originated from the fractional crystallization of tholeiitic basalt melts as cumulates, and the komatiites originated from high-degree melting of the mantle plume tail with garnet entering the melt phase. These high-Mg lavas erupted in a continental rift when the mantle plume impinged on the continental lithosphere, generating rifting and subsequent volcanic eruptions. These ultramafic–mafic rocks (3.2–3.0 Ga) formed the HGB, which was subsequently intruded by TTG (3.0–2.9 Ga), together forming the Archean Huangling granite–greenstone terrane in the Yangtze region.