| 晶粥储存、侵入体累积组装与花岗岩成因 |
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| 引用本文： | 马昌前,邹博文,高珂,文霞.晶粥储存、侵入体累积组装与花岗岩成因[J].地球科学,2020,45(12):4332-4351. |
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| 作者姓名： | 马昌前 邹博文 高珂 文霞 |
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| 作者单位： | 1.中国地质大学地球科学学院, 湖北武汉 430074 |
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| 基金项目： | 国家自然科学基金项目41972066 |
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| 摘 要： | 花岗质岩浆在地壳内的储存、迁移和分异,是导致大陆地壳生长演化的基本过程.有关地壳岩浆冷储存的新发现,挑战了数十年来深部存在以熔融体为主要组成的大岩浆房的观点.对活火山区的地球物理探测、岩石矿物学研究以及热历史模拟都一致证明,岩浆储库中的物质以晶粥为主,它们长时间处于固相线下的温度条件,属于冷储存状态.今天出露地表的大型侵入岩体,是古岩浆储库的代表,它们大都是在数百万年甚至更长的时间跨度内,多幕式的岩浆输运、累积侵位和多次添加组装而成的.侵入体的累积组装,可以通过岩石单元间接触关系的观察、岩石和矿物成分的不均一性研究以及侵入体内大的结晶时间跨度来证明.地壳浅部大型侵入体的形成,大体积的火山喷发,都要求存在穿地壳的岩浆通道系统,该系统中岩浆主要以岩墙形式将不同深度的岩浆储库串联起来,并通过无数岩床的堆垛而形成巨大的岩株或岩基等侵入体.高分异花岗岩和高硅流纹岩的存在,尤其是火山的超级喷发现象,要求岩浆储库的晶粥体发生活化和分异,而晶粥的解体往往是由于从下部侵入的新岩浆注入了额外的热和流体.保留在岩石中的晶体种群蕴含了侵入体累积组装、晶粥活化和岩浆分异的线索.尤其是再循环晶可以提供岩浆通道系统结构和演变的新信息.未来,在花岗岩成因研究中,重点要从晶粥活化与岩浆分异演化过程、岩浆上升和组装机制、火山岩与侵入岩的成因联系等方面入手,开展岩浆通道系统的跨学科研究,构建花岗岩岩浆过程研究的新范式,深入认识大陆地壳的生长和演化机理.
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| 关 键 词： | 晶粥 岩浆储库 岩浆通道系统 冷储存 累积组装 花岗岩类 |
| 收稿时间： | 2020-08-24 |
Crystal Mush Storage,Incremental Pluton Assemblyand Granitic Petrogenesis |
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| Abstract: | Storage,migration and differentiation of granitic magma in the crust are the basic processes leading to the growth and evolution of continental crust. Studies of magma storage and assembly in the crust over the past decade have challenged traditionally-held views of magma chambers as large,molten melt bodies. Geophysical exploration,petrological and mineralogical studies,and thermal history simulations in active volcanic areas have consistently demonstrated that the material in magma reservoirs is mainly crystal mush residing under sub-solidus temperature conditions for a long time and remaining in relatively cold storage. The large plutons outcropping on the surface today represent fossil magma reservoirs. Most of them were formed by multiple additions and incremental assembly of magma over a span of millions of years or even longer. The incremental assembly of plutons can be proved by observation of contact relationships between intrusive units,heterogeneity of rock and mineral compositions,and large timescales of pluton emplacement. The intrusion of large plutons in a shallow crust and large-volume volcanic eruptions require the existence of transcrustal magma plumbing systems in which magma is connected by a series of dykes to magma reservoirs at different depths,and huge stocks and batholiths are assembled by stacking of numerous sills.The existence of highly-fractionated granites and high-silica rhyolites,and especially the phenomena of super-eruptions require the reactivation and differentiation of crystal mush in magma reservoirs. The disaggregation of crystal mush is often due to a fresh magma intrusion from below injecting additional heat and fluid. The crystal cargo can provide clues to the pluton assembly,crystal mush rejuvenation and magma differentiation. In particular,antecrysts can provide new insights into the evolution of magma plumbing systems. In future,the study of granitic petrogenesis will focus on crystal mush rejuvenation and magma differentiation,the mechanisms of magma rise and assembly,the genetic relationships between volcanic rocks and intrusive rocks,and interdisciplinary research on magma plumbing systems,in order to construct a new paradigm for the study of granitic magma processes,and in-depth understanding of the growth and evolution mechanisms of continental crust. |
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