| 造山带橄榄岩岩石学与构造过程:以松树沟橄榄岩为例 |
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| 引用本文： | 张宏福,于红.造山带橄榄岩岩石学与构造过程:以松树沟橄榄岩为例[J].地球科学,2019,44(4):1057-1066. |
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| 作者姓名： | 张宏福 于红 |
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| 作者单位： | 1.西北大学地质学系大陆动力学国家重点实验室, 陕西西安 710069 |
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| 基金项目： | 大陆动力学国家重点实验室项目SKLCD-04国家自然科学基金委"创新研究群体"项目41421002 |
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| 摘 要： | 造山带橄榄岩不仅是地幔地球化学，而且是造山带形成与演化过程研究的主要对象.造山带橄榄岩主要有3种类型:（1）阿尔卑斯型橄榄岩，即岩石圈地幔构造-热侵位就位于造山带浅部地壳的橄榄岩；（2）前期层状基性-超基性堆晶岩经俯冲变质形成的橄榄岩；（3）蛇绿岩型橄榄岩.松树沟糜棱岩化橄榄岩及其相关高级变质岩详细的岩石学和地球化学研究发现这些橄榄岩记录了洋岩石圈形成到角闪岩相变质的全过程.即1 000~800 Ma洋岩石圈形成阶段，主要形成纯橄岩； < 800~500 Ma洋-陆转换即陆岩石圈演化阶段，岩石圈被交代形成大量方辉橄榄岩；500~480 Ma快速深俯冲和榴辉岩相变质阶段；460~335 Ma角闪岩相退变质阶段，此阶段在松树沟橄榄岩中形成大量富镁的直闪石类矿物，包括透闪石、阳起石和镁闪石.由此可见，蛇绿岩型造山带橄榄岩能够记录造山带形成与演化的全过程，通常会经历4个形成和演化阶段:（1）洋岩石圈（蛇绿岩）形成阶段，形成纯榄岩；（2）洋-陆转换阶段，陆岩石圈演化阶段，岩石圈受交代形成方辉橄榄岩；（3）岩石圈深俯冲，榴辉岩相变质；（4）俯冲板片抬升至角闪岩相时退变质，此时在橄榄岩中形成富镁的直闪石类矿物.不同造山带中蛇绿岩型橄榄岩的区别可能只是俯冲深度和退变质程度不同而已.最后，蛇绿岩一定要强调是什么时代的蛇绿岩.同时，造山带进变质作用产物经常会被后期抬升过程中退变质作用彻底改造，这应该引起重视.
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| 关 键 词： | 造山带橄榄岩 交代方辉橄榄岩 岩石圈深俯冲 角闪岩相退变质 蛇绿岩 岩石学 |
| 收稿时间： | 2018-09-23 |
Petrological and Tectonic Evolution of Orogenic Peridotite Massif: A Case of Songshugou Peridotites |
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| Abstract: | Orogenic peridotite is one of major research targets not only for mantle geochemistry, but also for the formation and evolution of the orogenic belts. There are mainly three types of orogenic peridotites: (1) Alpine peridotite, i. e. lithospheric mantle tectonic-thermal diaper into the shallow orogenic crust; (2) mafic-ultramafic cumulates of layered intrusions underwent subduction and metamorphism; (3) ophiolitic peridotite.Detailed petrological and geochemical investigation on Songshugou mylonitized peridotites and their related high-grade metamorphic rocks demonstrates that the Songshugou peridotites recorded the whole cycle from the formation of an oceanic lithosphere to amphibolite-facies retrograde metamorphism. i. e. dunites produced during the formation of an oceanic lithosphere at 1 000-800 Ma; followed by the period of oceanic-continental transition during < 800-500 Ma, lithospheric dunites metasomatized to produce an amounts of metasomatic harzburgites; rapid deep subdution and eclogite-facies metamorphism at 500-480 Ma; and amphibolite-facies retrograde metasomatism during slow exhumation at 460-335 Ma, magnesium-rich anthophyllites in Songshugou peridotites, including tremolite, actinolite, and magnesium amphibole, were emerged at this stage.Thus it can be seen that ophiolitic orogenic peridotites can record the whole cycle from the orogen formation and its evolution.They often underwent four stages:(1) formation of an oceanic lithosphere (ophiolite) to produce dunites; (2) the period of oceanic-continental transition and the formation of metasomatic harzburgite due to mantle metasomatism; (3) deep lithosphere subduction and eclogite-facies metamorphism; (4) retrograde metamorphism when exhumed to the depth of amphibolite-facies, lots of anthophyllites in peridotites emerged in this stage. Different orogens may have a diverse rock types just in the depth of the deep subduction and in degrees of retrograde metamorphism. Finally, the age formation of ophiolites must be emphasized.Meantime, the high grade metamorphosed rocks can be completely destroyed due to the later retrograde metamorphism, this deserves a great attention. |
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