【作者】 陈杰；

【导师】 杨明慧；

【作者基本信息】 中国石油大学(北京) ， 地质学， 2024， 博士

【摘要】 华北克拉通参与了中元古代Columbia超大陆的裂解过程,同期构造-沉积-岩浆事件蕴含着能够揭示前寒武纪构造演化乃至板块构造活动规律的重要信息。华北克拉通南部发育多个裂陷槽和多期岩浆活动,是解析中元古代构造体制转变和裂解事件的理想地区。再者,明确克拉通南部裂陷槽的构造和沉积充填特征也将为中国前寒武纪深层油气勘探领域提供重要的地质证据。据此,本文抓住华北克拉通南部中元古代裂陷事件形成演化过程这一关键问题,基于地球物理学、地球化学和地质学等多学科交叉研究,系统分析了中元古代构造-沉积-岩浆活动的特征,厘定了裂陷事件的演化序列,深入探讨其对Columbia超大陆裂解过程的响应。本文取得以下几点认识:(1)重磁5阶细节异常场是华北克拉通南部中元古界重磁异常场的反应。晋陕地区以NE向断裂为主,NW向次级断裂为辅,具半地堑构造样式和隆坳相间的构造格局。熊耳裂陷槽呈三叉裂谷形态,向北延伸至沁水盆地,其内发育NNE向断裂,具对称地堑构造样式。晋陕和熊耳裂陷槽分别与鄂尔多斯地块内微陆块拼合带和中部造山带存在空间叠合,其形成演化可能与基底先存断裂带活化有关。(2)晋陕裂陷槽沉积地层整体存在自SW-NE向逐渐减薄的特征,熊耳裂陷槽沉积地层则存在自南向北逐渐减薄特征。裂陷槽充填过程可划分为四个阶段:长城纪早期火山-沉积充填阶段(1.80～1.75 Ga)、长城纪持续海侵阶段(1.75～1.60Ga)、蓟县纪稳定沉积阶段(1.6～1.4 Ga)和待建纪区域隆升阶段(1.4～1.0 Ga)。(3)熊耳群许山组、鸡蛋坪组和马家河组火山岩以及邻区基性岩墙岩浆结晶年龄分别为:1783±20 Ma、1777±20 Ma、1764±13 Ma和1781±20 Ma。该套中-基性岩浆岩以部分熔融为主,可能经历了一定程度的分离结晶,其构造背景多指示陆内裂谷,可能与熊耳地幔柱活动有关。保家山花岗岩、龙王(石童)花岗岩以及栾川熊耳群流纹岩这三个酸性岩浆岩的结晶年龄分别为:1803±29 Ma、1607±21 Ma和1776±16 Ma,表现出A型花岗岩/流纹岩的亲缘性,其来源于古老地壳的部分熔融,指示造山后伸展和非造山/陆内裂谷的构造背景。(4)南部中元古代岩浆事件可划分为三期:1.80～1.78 Ga侵入岩岩浆事件Ⅰ、1.78～1.75 Ga熊耳火山事件、1.63～1.60 Ga侵入岩岩浆事件Ⅱ,整体具有造山后伸展、陆内裂谷和非造山/陆内裂谷的演化序列。(5)综合华北克拉通南部中元古代构造-沉积-岩浆特征和演化序列可将南部裂陷槽演化过程整体划分为三个阶段:裂前隆升剥蚀阶段(1.80～1.78 Ga)、同裂谷持续伸展阶段(Ⅰ期:1.78～1.60 Ga和Ⅱ期:1.6～1.4 Ga)和裂后隆升剥蚀阶段(1.4～1.0 Ga)。(6)华北克拉通参与了Columbia超大陆的裂解过程。时间上,熊耳火山岩和同期基性岩墙于～1.78 Ga开始大规模发育指示超大陆开始裂解;1.78～1.60 Ga南部陆内裂谷演化为被动大陆边缘,指示克拉通南部已彻底裂解;1.6～1.4 Ga克拉通南部裂解强度减弱且逐渐处于热冷却沉降阶段,指示超大陆裂解过程已逐渐处于尾声。空间上,克拉通南部中元古代的火山-沉积充填地层形成于造山后伸展-陆内裂谷背景,指示其裂解位置在超大陆内部而非边缘,并可能与印度克拉通相连。机制上,地幔柱作用是华北克拉通南部中元古代裂解的主要原因,指示超大陆裂解可能主要经历了自下而上的裂解过程。更多还原

【Abstract】 The North China Craton participated in the breakup process of the Mesoproterozoic Columbia supercontinent,and contemporaneous tectonic,sedimentary,and magmatic events contain important information that reveals the tectonic evolution and plate tectonic movement patterns of the Precambrian.The southern North China Craton has developed multiple rifts and multi-stage magmatic activities,which is an ideal area for further analysis of the Mesoproterozoic tectonic regime transformation and breakup events.Furthermore,clarifying the tectonic characteristics and sedimentary patterns of the rift in the southern North China Craton will also provide important geological evidence for the Precambrian deep oil and gas exploration in China.Based on this,this paper grasps the key issue of the formation and evolution process of the Mesoproterozoic rifting event in the southern North China Craton.Based on the interdisciplinary research of geophysical analysis,geochemistry,and regional tectonic analysis,this paper systematically analyzes the characteristics of the Mesoproterozoic tectonic-sedimentary-magmatic activity,determines the evolution sequence of the southern rifting event,and deeply discusses its response to the Columbia supercontinent cracking process.This study has achieved the following understandings:(1)The fifth-order detailed gravity and magnetic anomaly field is the response of the Mesoproterozoic gravity and magnetic anomaly field in the southern North China Craton.The Jinshaan rift is dominated by NE-trending faults,and the NW-trending secondary faults crosscut,with a half-graben structural style and a structural pattern of alternating uplifts and depressions.The Xiong’er rift is in the form of a trident rift,extending northward to the Qinshui basin,where NNE-trending faults are developed,with a symmetrical graben structural style.The Jinshaan and Xiong’er rifts are spatially superimposed with the micro-continental block suture zone in the Ordos block and the central orogenic belt,respectively,and their formation and evolution may be related to the activation of pre-existing basement fault zones.(2)The sedimentary strata of the Jinshaan rift have a gradually thinning feature from southwest to northeast,while the sedimentary strata of the Xiong’er rift have a gradually thinning feature from south to north.The filling process of the rifts can be divided into four stages:the early volcanic sedimentary filling stage of the Changcheng period(1.80-1.75 Ga),the continuous marine invasion stage of the Changcheng period(1.75-1.60 Ga),the stable sedimentary stage of the Jixian period(1.6-1.4 Ga),and the regional uplift stage of the Ectasian period(1.4-1.0 Ga).(3)The crystallization ages of the volcanic rocks of the Xushan Formation,Jidanping Formation,and Majiahe Formation of the Xiong’er Group and the basic dykes in the adjacent area are 1783±20 Ma,1777±20 Ma,1764±13 Ma and 1781±20 Ma,respectively.This set of intermediate-basic magmatic rocks is dominated by partial melting,which may have experienced a certain degree of separation and crystallization.Its tectonic background mostly indicates an intracontinental rift,which may be related to the activity of the Xiong’er mantle plume.The crystallization ages of the three acidic magmatic rocks of the Baojiashan granite,the Longwang granite and the Xiong’er group rhyolite in Luchuan are 1803±29 Ma,1607±21 Ma and 1776±16 Ma,respectively,showing the affinity of A-type granite/rhyolite,which is derived from the partial melting of the ancient crust,indicating the tectonic background of post-orogenic extension and non-orogenic/intracontinental rift.(4)The Mesoproterozoic magmatic events in the southern region can be divided into three stages:1.80-1.78 Ga intrusive magmatic events I,1.78-1.75 Ga Xiong’er volcanic rocks,and 1.63-1.60 Ga intrusive magmatic events II.The overall evolution sequence includes post-orogenic extension,intracontinental rift,and non-orogenic/intracontinental rift.(5)Based on the Mesoproterozoic tectonic-sedimentary-magma characteristics and evolution sequence of the southern craton,the evolution process of the southern rifts can be divided into three stages:pre-rift uplift and denudation stage(1.80-1.78 Ga),syn-rift continuous extension stage(stage I:1.78-1.60 Ga and stage II:1.6-1.4 Ga)and post-rift uplift and denudation stage(1.4-1.0 Ga).(6)The North China Craton participated in the breakup of the Columbia supercontinent.Temporally,the large-scale development of Xiong’er volcanic rocks and basic dykes at～1.78 Ga indicates that the supercontinent began to break up.At1.78-1.60 Ga,the southern intracontinental rift evolved into a passive continental margin,indicating a complete breakup of the southern craton.The 1.6-1.4 Ga cratonic southern breakup intensity is weakened and gradually in the stage of thermal cooling subsidence,indicating that the supercontinent breakup process has gradually come to an end.Spatially,the Mesoproterozoic volcanic-sedimentary strata in the southern craton were formed in the post-orogenic extensional-intracontinental rift background,indicating that the breakup location was within the supercontinent rather than the margin,which may be connected with the Indian craton.In terms of mechanism,the mantle plume is the main reason for the Mesoproterozoic breakup in the southern craton,indicating that the supercontinent breakup may have mainly experienced a bottom-up breakup process.更多还原