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    华北中部古元古代末期构造-热事件性质及其构造成因模式

    Nature of the latest Paleoproterozoic tectono-magmatic event in central North China and its tectonic genetic model

    • 摘要: 提要:古元古代末期为华北克拉通演化的重大转折时期,但这一时期重大构造热事件序列及其构造格局的研究较薄弱。笔者在区域构造分析基础上,结合最新的同位素年龄制约,探讨古元古代末期区域构造演化过程及其成因模式。太行山—恒山基性岩墙群对应于燕辽坳拉谷与太行坳拉谷的夭折支,它们共同构成非对称的三叉坳拉谷系。 非造山的岩浆活动序次依次为:花岗岩、伟晶岩(1.85~1.80 Ga)、基性岩墙群侵位(1.80~1.77 Ga)、斜长岩、碱性花岗岩、环斑花岗岩(1.71~1.70 Ga)、火山岩喷发(1.68 Ga)等。下伏基底性质对比及其同位素年龄表明,18亿年前后燕辽—太行山地区发生大规模隆升,隆升范围达上千千米,核心区处于燕辽—太行山坳拉谷系中心位置。基底隆升事件与浅表层伸展构造-非造山岩浆活动在时空上相吻合,表明地幔柱模式可以合理解释上述区域隆升及其伸展裂解事件。

       

      Abstract: Abstract:The latest Paleoproterozoic Period represents one of the most important transition stages of the evolution of the North China craton, but its relevant tectonothermal episodes and tectonic framework are rarely documented in detail. In this paper, the tectonic evolution and genetic model are discussed based on the regional tectonic analysis, combined with the latest isotopic age dating. The NW-trending Taihang-Hengshan mafic dike swarms (1.80-1.77 Ga) correspond to failed arms of the Yanliao and Taihang aulacogens, which formed an asymmetric aulacogen system with triple arms. The relevant anorogenic magmatism consists (in order of time) of granite and pegmatite intrusion (1.85-1.80 Ga), injection of basic dike swarms (1.80-1.77Ga), anorthosite,alkaline granite and rapakivi granite intrusion (1.71-1.70 Ga) and volcanic eruption (1.68 Ga). As indicated by the regional correlation of the underlying basement complexes and isotopic age dating, large-scale domal uplift took place in the Yanliao-Taihang area at ~1.80 Ga, with an uplift diameter up to 1000 km. The core area of the domal uplift is located at the center of the Yaoliao-Taihang aulacogen system. The uplift of the basement coincided with the supracrustal extension structures and anorogenic magmatism in time and space, which supports the mantle plume model for a rational interpretation of the above-mentioned regional uplift and extensional break-up event in the latest Paleoproterozoic episodes of the North China carton.

       

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