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Petrology and geochemistry of the Archean Huangling greenstone belt in the Yangtze Craton, South China
Precambrian Research ( IF 3.2 ) Pub Date : 2021-08-17 , DOI: 10.1016/j.precamres.2021.106340
Junqi Wei 1
Affiliation  

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.



中文翻译:

华南扬子克拉通太古代黄陵绿岩带岩石学和地球化学

太古宙黄陵绿岩带(HGB)在扬子克拉通黄陵花岗岩-绿岩地体中以角闪岩形式保存。在地质和地球化学上,角闪岩为变质火山岩,可细分为角闪岩片岩、块状角闪岩和带状角闪岩,分别为科马提岩、科马提质玄武岩和拉斑玄武岩原岩。科马提岩具有高 MgO(20-30%)、Cr、Co 和 Ni 含量;Rb、Sr、Ba 和 ΣREE 含量低;和轻微的 LREE 消耗和 HREE 富集,根据标准 (CaO/Al 2 O 3 ) adj  ˃ 20, (Al 2 O 3 /TiO 2 ) adj和 (Gd/Yb) PM 将它们表征为 Al 未耗尽型 < 1. 科马提质玄武岩和拉斑玄武岩的 MgO(5-16%)、Cr、Co 和 Ni 含量较低;较高的 Rb、Sr、Ba 和 ΣREE 含量;和轻微的 LREE 富集和 HREE 消耗。地球化学图(Zr/Y vs. Nb/Y、Nb/Yb vs. Th/Yb、La/Ta vs. La/Sm 和 Y vs. Zr/Y)、负 Nb 异常、宽 Ɛ Nd值 (-8.0至 +6.2)、负锆石 Ɛ Hf值(-11.59 至 -3.98)和旧 T Nd (DM) (3.9–2.9 Ga) 和锆石 T Hf角闪岩的 (DM) 年龄 (3.9-3.3 Ga) 反映了地幔源具有轻微的地壳污染,表明科马提质玄武岩和拉斑玄武岩之间的关系比科马提岩更密切。拉斑玄武岩起源于地幔柱头的中等程度熔融,科马提质玄武岩起源于拉斑玄武岩熔体分步结晶为堆积物,科马提岩起源于地幔柱尾的高度熔融,石榴石进入熔融相. 当地幔柱撞击大陆岩石圈时,这些高镁熔岩在大陆裂谷中喷发,产生裂谷和随后的火山喷发。这些超基性-基性岩(3.2-3.0 Ga)形成了HGB,随后被TTG(3.0-2.9 Ga)侵入,

更新日期:2021-08-17
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