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Felsic Igneous Rocks in the Hua'aobaote Pb-Zn-Ag Polymetallic Orefield, Southern Great Xing'an Range: Genesis, Metallogenetic and Tectonic Significance
Acta Geologica Sinica-English Edition ( IF 3.5 ) Pub Date : 2021-05-31 , DOI: 10.1111/1755-6724.14729
Zhi SHANG 1 , Yongqing CHEN 1 , Xiangguo GUO 1, 2
Affiliation  

The Hua'aobaote Pb-Zn-Ag Polymetallic orefield is situated in the southern section of the Great Xing'an Range (GXAR), which has experienced extensive magmatism. Since the Paleozoic, there are two stages of magmatism in Hua'aobaote orefield occurred in the Paleozoic and Mesozoic. The Mesozoic magmatism is of great significance for the Pb-Zn-Ag Polymetallic mineralization in Hua'aobaote orefield. In this study, new geochemical data was obtained to discuss the timing and petrogenesis of the magmatic rocks and its geodynamic and metallogenic significance. Zircon U-Pb ages reveal that the felsic igneous rocks from the Hua'aobaote orefield were formed in the Early Permian (294.8 ± 3.2 Ma) and Early Cretaceous (132.6 ± 1.4 Ma). Geochemically, the Early Permian granodiorite porphyrite is characterized by high Sr/Y (42–63) ratios and Mg# (62.24–70.74) values and low heavy rare earth element (HREE) (5.09–6.79 ppm) contents. The granodiorite porphyrite is also characterized by depleted Sr–Nd initial isotopic signatures [Nd(t) = 5.91–7.59, (87Sr/86Sr)i = 0.7029–0.7030], exhibiting adakitic characteristics. The Early Cretaceous granite porphyry and rhyolite are A-type felsic igneous rocks, and demonstrate high SiO2, Na2O + K2O and rare earth element (REE) contents, low CaO and MgO contents, low (87Sr/86Sr)i ratios (0.7044–0.7058), and positive Nd(t) values (2.57–4.65). Whole-rock Pb isotopic compositions in granodiorite porphyrite are: 206Pb/204Pb = 17.631–18.149, 207Pb/204Pb = 15.422–15.450, and 208Pb/204Pb = 37.325–37.729. The granite porphyry and rhyolite have initial 206Pb/204Pb, 207Pb/204Pb, and 208Pb/204Pb ratios of 18.106–19.309, 15.489–15.539, and 37.821–38.05, respectively. Sr-Nd-Pb isotopic evidence suggests that the Early Permian granodiorite porphyrite is likely to derive from slab melts and modified by peridotitic mantle wedge in the subduction tectonic setting of the Paleo-Asian Ocean. The Early Cretaceous A-type felsic igneous rocks were derived from juvenile lower crust, accompanied by limited crustal contamination and various degree of fractional crystallisation during magma emplacement. The Early Cretaceous magmatism and related mineralization were formed in a post-orogenic tectonic setting that attributed to the closure of the Mongol–Okhotsk Ocean. Pb isotopic data for the various rock units in the study area indicate that the Mesozoic magma source contributed substantial Pb, Zn, and Ag to the Hua'aobaote deposit.

中文翻译:

大兴安岭南部华澳宝特铅锌银多金属矿田长英质火成岩:成因、成矿及构造意义

华澳宝特铅锌银多金属矿田位于大兴安岭南段,经历了广泛的岩浆活动。自古生代以来,华澳宝特矿田发生了古生代和中生代两个阶段的岩浆作用。中生代岩浆作用对华澳宝特矿区铅锌银多金属成矿具有重要意义。在这项研究中,获得了新的地球化学数据,讨论了岩浆岩的成因和成因及其地球动力学和成矿意义。锆石U-Pb年龄揭示华澳宝特矿区长英质火成岩形成于早二叠世(294.8±3.2 Ma)和早白垩世(132.6±1.4 Ma)。地球化学上,早二叠世花岗闪长玢岩具有高 Sr/Y(42-63)比和 Mg# (62.24–70.74) 值和低重稀土元素 (HREE) (5.09–6.79 ppm) 含量。花岗闪长玳岩还具有贫Sr-Nd初始同位素特征[ Nd (t) = 5.91-7.59, ( 87 Sr/ 86 Sr) i = 0.7029-0.7030],表现出埃达克质特征。早白垩世花岗斑岩和流纹岩为A型长英质火成岩,SiO 2、Na 2 O + K 2 O和稀土元素(REE)含量高,CaO和MgO含量低,(87 Sr/ 86 Sr ) i比率 (0.7044–0.7058),和正Nd(t) 值 (2.57–4.65)。花岗闪长玢岩全岩Pb同位素组成为:206 Pb/ 204 Pb = 17.631~18.149、207 Pb / 204 Pb = 15.422~15.450、208 Pb / 204 Pb = 37.325~37.729。花岗斑岩和流纹岩初始有206 Pb/ 204 Pb、207 Pb/ 204 Pb和208 Pb/ 204铅比率分别为 18.106–19.309、15.489–15.539 和 37.821–38.05。Sr-Nd-Pb同位素证据表明早二叠世花岗闪长玳岩很可能来源于板片熔体,并在古亚洲洋俯冲构造环境中受到橄榄岩地幔楔的修饰。早白垩世A型长英质火成岩来源于幼年下地壳,在岩浆侵位过程中伴有有限的地壳污染和不同程度的分级结晶。早白垩世岩浆作用和相关矿化形成于后造山构造环境,归因于蒙古-鄂霍次克洋的闭合。研究区各岩石单元的Pb同位素数据表明,中生代岩浆源对华澳宝特矿床贡献了大量的Pb、Zn和Ag。
更新日期:2021-05-31
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