新时代花岗岩的新理论:花岗岩四阶段理论探讨  

A new granitization theory:Discussion on the four-stage granitization theory

作　　者：张旗[1,2] 翟明国[1,2] 魏春景[3] 周李岗 黄广宇 陈万峰 焦守涛 汤军[7] 刘睿 原杰 王振 王跃[11] 袁方林 ZHANG Qi;ZHAI Mingguo;WEI Chunjing;ZHOU Ligang;HUANG Guangyu;CHEN Wanfeng;JIAO Shoutao;TANG Jun;LIU Rui;YUAN Jie;WANG Zhen;WANG Yue;YUAN Fanglin(Institute of Geology and Geophysics,Chinese Academy of Sciences,Beijing 100029,China;State Key Laboratory of Lithospheric Evolution,Beijing 100029,China;School of Earth and Space Sciences,Peking University,Beijing 100871,China;Key Laboratory of Mineral Resources in Western China(Gansu Province),School of Earth Sciences,Lanzhou University,Lanzhou 730000,China;Natural Resources Survey of China Geological Survey,Beijing 100055,China;Development Research Center of China Geological Survey,Beijing 100037,China;School of Earth Sciences,Yangtze University,Wuhan 430100,China;School of Resources and Environmental Engineering,Shandong University of Technology,Zibo 255000,China;School of Resources and Environment,Xingtai University,Xingtai 054001,China;Institute of Geology,Chinese Academy of Geological Sciences,Beijing 100037,China;School of Earth Sciences and Resources,China University of Geosciences(Beijing),Beijing 100083,China)

机构地区：[1]中国科学院地质与地球物理研究所,北京100029 [2]岩石圈演化国家重点实验室,北京100029 [3]北京大学地球与空间科学学院,北京100871 [4]兰州大学地质科学与矿产资源学院甘肃省西部矿产资源重点实验室,甘肃兰州730000 [5]中国地质调查局自然资源综合调查指挥中心,北京100055 [6]中国地质调查局发展研究中心,北京100037 [7]长江大学地球科学学院,湖北武汉430100 [8]山东理工大学资源与环境工程学院,山东淄博255000 [9]邢台学院资源与环境学院,河北邢台054001 [10]中国地质科学院地质研究所,北京100037 [11]中国地质大学(北京)地球科学与资源学院,北京100083

出　　处：《地学前缘》2023年第6期406-435,共30页Earth Science Frontiers

基　　金：自然资源部深地科学与探测技术实验室开放课题“下地壳底部填图理论与方法探索(202211)”;国家自然科学基金重大项目(41890834);国家自然科学基金项目“大数据环境下的滑坡危险性评估模型构建方法研究(41872253)”;中国科学院重点项目(QYZDY-SSWDQc017,41000000);国家重点研发计划项目“基于地质云的地质灾害基础信息提取与大数据分析挖掘(2018YFC1505501)”和“基于‘地质云’平台的深部找矿知识挖掘(2016YFC0600510)”;中国地质调查局项目“地球科学数据集成与服务(DD20221785)”。

摘　　要：花岗岩的成因既是古老的问题,也是当前急迫的科学前沿。100年前花岗岩的火成论与变成论之争,以火成论压倒变成论而收兵。近百年的研究证明,火成论并非完美,关键是玄武岩浆分离结晶成花岗岩的机理受到严峻的挑战。而今,花岗岩源自下地壳变质出熔已经成为不争的事实,说明花岗岩的源头是变质岩。关于花岗岩成因的理论很多,经过多年的筛选,可能花岗岩形成的四阶段理论(从产生、分凝、上升到侵位)是比较合适的。在对该理论详细研究的基础上,本文提出了一个新的花岗岩四阶段理论:从产生、形成、上升到侵位。这是对花岗岩形成过程的描述。如果强调花岗岩形成的机理,则可表述为从出熔、聚集、上升到侵位。四个阶段分为两段:产生和形成(出熔和聚集)是升温过程;上升和侵位是降温过程。该理论的核心是本文提出的“下地壳岩浆房”的猜想,这指的是由部分熔融产生的熔体经聚集形成的巨大空间。首先,这个猜想解决了下地壳岩浆的空间占位问题。由于下地壳原地部分熔融熔出的产物(熔体+残留体)仅仅是物质组成形式发生了变化,不存在空间占位问题,下地壳总体积基本不变。只要存在持续的地幔加热过程,岩浆房体积可以逐渐增大一直到变得非常大。其次,关于花岗岩上升的驱动力问题,我们认为,可能正是下地壳岩浆房上覆的几十公里厚的地层静压力,在岩浆房沿着破裂带溢出时转换为巨大的压力驱使岩浆向上运移,而非岩浆自身的浮力。因此,从理论上,花岗岩上升的速度是非常快的,地质上几乎是瞬间实现的。再次,本理论还合理地解释了花岗岩侵位空间这个古老的难题:下地壳岩浆房上升移出,原先的空间即刻被上覆地层压实填充,造成上覆地层的塌陷,并传递到脆性的上地壳;同时引起上地壳支撑薄弱部位出现构造真空,为上升的岩浆�The origin of granite is both an ancient and a frontier scientific problem.One hundred years ago debate on the origin of granite ended with the prevailing view that granite is igneous rather than metamorphic in origin.However,over the past century researchers have shown that the igneous theory is not perfect and the mechanism of basalt crystallization differentiation into granite had been severely challenged.Today it is considered an indisputable fact that granite originated from partial melting of the lower crust,which indicates the source of granite is metamorphic rock.There are many theories on the formation of granites.After many years of testing,the four-stage(melting,melt segregation and ascent,and magma emplacement)theory of granite formation is considered more plausible.Based on detailed study of this theory,this paper proposes a new four-stage theory which divides the granite formation process into two main parts:melt generation and formation(melting and melt aggregation),a heating process,and melt ascent and magma emplacement,a cooling process.The core of this theory is the conjecture of a“lower crustal magma chamber”,which refers to the giant space formed by melt aggregation.This conjecture,first,solves the space problem of a magma chamber in the lower crust.As in situ partial melting of the lower crust only changes the material composition of its products(melt plus remnant),with no space issue involved,the total volume of the lower crust is basically unchanged.And,as there is continuous mantle heating,a lower crustal magma chamber can grow gradually and become very large.Second,we consider the driving force behind magma uplift is not the buoyancy of magma itself.Rather,as the lower crustal magma chamber overflows along the fault zone,the formation pressure from tens of kilometers of strata beneath the magma chamber may transform into great force,driving the magma upward.Therefore,theoretically,granite can rise very quickly,almost instantaneously on the geologic time scale.Third,this conjecture rea

关 键 词：花岗岩 四阶段理论 下地壳岩浆房 塌陷模式 变质岩浆岩石学 物理地质学 

分 类 号：P588.121[天文地球—岩石学]