| 李 赛.华南中生代玄武岩地球化学特征及其地球动力学意义[J].地质与勘探,2022,58(5):1001-1015 |
| 华南中生代玄武岩地球化学特征及其地球动力学意义 |
| Geochemical characteristics and geodynamic significance of Mesozoic basalts in South China Block |
| 投稿时间：2022-05-02 修订日期：2022-07-07 |
| DOI：10.12134/j.dzykt.2022.05.008 |
| 中文关键词: 华南板块 岩石圈演化 中生代玄武岩 古太平洋俯冲板块 有色金属 稀有金属 |
| 英文关键词: South China Block (SCB), lithospheric evolution, Mesozoic basalts, Paleo-Pacific subducted plate, non-ferrous metals, rare metals |
| 基金项目:湖南省自然科学基金（编号：2017JJ3261）、创新项目（编号：202110555075；X202010555338）和南华大学人才项目（编号：2018XQD22）联合资助 |
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| 中文摘要: |
| 华南板块，作为中国东部岩石圈的重要组成部分，广泛发育中生代玄武岩。这些玄武岩为研究华南岩石圈演化提供了重要的窗口。虽然前人对华南中生代玄武岩开展了大量的研究，但是对于玄武岩的源区性质以及构造环境等认识仍存在较大争议。本文系统性地分析了华南宁远、道县、长城岭、白面山、汝城等地区中生代玄武岩的主微量元素及Sr-Nd-Pb同位素组成，获得如下主要认识：（1）华南中生代玄武岩主要由碱性和亚碱性玄武岩组成，其SiO2和全碱（Na2O+K2O）含量分别为42.81～55.54 wt％和1.6％～5.97 wt％；（2）除了宁远玄武岩具有OIB微量元素特征，华南中生代玄武岩具有岛弧玄武岩相似的微量元素配分型式；（3）主量和微量元素特征表明华南中生代玄武岩的形成主要受控于部分熔融，且在岩浆演化过程中经历过不同程度的分离结晶作用，未遭受明显的地壳混染作用。Ni-MgO正相关、CaO/Al2O3-CaO正相关和Eu无明显异常表明华南中生代玄武质岩浆经历了橄榄石和单斜辉石结晶，但无明显的斜长石结晶；（4）Sr-Nd-Pb同位素特征表明华南中生代玄武岩为EMⅡ地幔源区，其源区可能有洋壳沉积物的参与；（5）华南中生代玄武岩可能形成于与古太平洋板块俯冲相关的大陆板内环境；（6）华南岩石圈改造可能与中生代古太平洋俯冲板块的交代作用有关，后者所释放的酸性熔体/流体与地幔橄榄岩相互作用，最终造成了华南岩石圈物理化学性质的强烈改变；（7）古太平洋俯冲板块可能对华南有色金属、稀有金属等多金属成矿发挥着重要作用，其释放的熔体或流体为矿石活化和迁移提供了重要的驱动力。本文对于认识华南多金属成矿作用的理论与应用研究具有重要意义。 |
| 英文摘要: |
| The South China Block (SCB), as an important part of the lithosphere in the eastern China, has extensive distribution of Mesozoic basalts. These basalts provide an important window to reveal the lithospheric evolution of the SCB. Although previous researchers have extensively studied the Mesozoic basalts from the SCB, but haven’t reached consensus on the understanding of the magma source and tectonic setting of these basalts. In this paper, the major and trace elements and Sr-Nd-Pb isotopic compositions of the basalts from the typical regions in the SCB, such as Ningyuan, Daoxian, Changchengling, Baimianshan, Rucheng, were systematically analyzed, and the following main understandings were obtained: (1) The Mesozoic basalts in the SCB are mainly alkaline and sub-alkaline basalts, with the SiO2 and total alkali (Na2O+K2O) contents of 42.81% ~ 55.54 wt% and 1.6% ~ 5.97 wt%, respectively. (2) Except for the Ningyuan basalts with OIB-like trace element features, the Mesozoic basalts from the SCB have the distribution patterns resembling the island arc basalts. (3) The characteristics of major and trace elements show that the formation of Mesozoic basalts from the SCB was mainly controlled by partial melting, and experienced different degrees of fractional crystallization during the magmatic evolution process, with no obvious crustal contamination. The positive correlation of CaO/Al2O3-CaO and Ni-MgO, as well as no obvious abnormality of Eu indicate that the Mesozoic basaltic magma might experience olivine and clinopyroxene, but no significant plagioclase crystallization. (4) The Sr-Nd-Pb isotopic characteristics of the Mesozoic basalts from the SCB indicate that these basalts originated from EMII mantle, with possible involvement of oceanic crust sediments; (5) The Mesozoic basalts from the SCB might be formed in the intraplate setting related to the subduction of the Paleo-Pacific plate. (6) The lithospheric transformation of the SCB may be related to the metasomatism of the Mesozoic subducted paleo-Pacific plate, from which the acidic melts/fluids released interacted with the mantle peridotite, consequently resulting in drastic change in the physical and chemical properties of the lithosphere beneath the SCB. (7) The paleo-Pacific subducted plate may play an important role in the mineralization of polymetallic metals such as non-ferrous metals and rare metals in south China; the released melts or fluids provide an important driving force for the ore activation and migration. This paper is of important significance for the theoretical and applied studies on understanding the polymetallic mineralization in South China. |
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