南非林波波带中央带Sand River地区麻粒岩相变质作用研究
发布时间：2019-01-18 07:59
【摘要】：南非林波波带位于卡普瓦尔克拉通与津巴布韦克拉通之间,是世界著名的太古代到早元古代的经过多期构造事件和高级变质的构造带。林波波带根据其构造和岩石组合特征,可进一步划分为北边缘带、中央带和南边缘带。中央带麻粒岩相尤其是高压麻粒岩相变质岩石的研究受到国内外学者广泛关注,尤其林波波带中央带变质作用P-T轨迹及林波波带构造演化存在很多争论。本文通过对南非林波波带中央带Sand River地区基性麻粒岩的研究,来探讨林波波带中央带Sand River地区基性麻粒岩的成因及林波波带中央带构造演化历史。Sand River地区位于南非林波波带中央带东北部,对南非林波波带中央带Sand River地区麻粒岩相岩石进行了岩相学、传统地质温压计、变质相平衡、地球化学及变质作用等方面的初步研究可得,该麻粒岩原岩类型为岛弧拉斑玄武岩,其变质作用演化可划分三个不同的变质阶段:(1)峰期高压变质阶段;(2)早期退变质阶段;(3)晚期退变质阶段。峰期(M1)的矿物组合为Grt+Cpx+Qtz+Ilm+Mag;早期退变质(M2)矿物组合是Opx+Pl±Grt±Cpx+Qtz,;晚期退变质(M3)矿物组合是Amph+Pl±Opx±Grt±Cpx+Qtz,。退变质作用PTt轨迹为顺时针型近等温降压到降温降压的过程。传统地质温压计估算得到峰期(M1)变质温压条件为T=820-900℃,P=13.5-15.4kbar;早期退变质(M2)形成温压为800-890℃和8.8-11.2kbar;晚期退变质(M3)温压条件为540-650℃和2.7-4.4kbar。相平衡模拟得到峰期高压变质区(M1区)温压条件为T=810-890℃,P=12.5-14.5kbar;早期退变质区(M2区)变质温压条件为T=830-880℃,P=6.5-7.5kbar;晚期退变质区(M3区)变质温压条件为T=580-670℃,P=4.5-5.5kbar。两种方法估算的变质作用PT结果基本一致。本研究认为林波波带中央带Sand River地区麻粒岩可能形成于20亿年前后,与津巴布韦克拉通与卡普瓦尔克拉通陆陆碰撞过程中的地壳加厚有关,岩体在经历地壳加厚及麻粒岩相变质之后,由于构造运动,被快速抬升到了地壳浅部,从而发育了近等温降压(ITD)的退变质PTt轨迹。在地壳浅部层位,岩体又可能受到了流体的影响,从而经历了晚期的角闪岩相变质作用。
[Abstract]:The South African Limbowave belt is located between the Cape Walcraton and the Zimbabwe Craton. It is a world famous Archean to early Proterozoic tectonic event and high grade metamorphic tectonic belt. According to the characteristics of structure and rock assemblage, the limbo wave zone can be further divided into three zones: the northern marginal zone, the central zone and the southern marginal zone. The study of granulite facies in central zone, especially high-pressure granulite facies metamorphic rocks, has been widely concerned by scholars at home and abroad, especially the P-T locus of the central zone metamorphism and the structural evolution of the Limbowave zone. In this paper, the basic granulites in the Sand River region of the central zone of the South African Limbo Wave Zone are studied. The origin of basic granulites in the Sand River area of the central zone of the Limbo wave belt and the history of tectonic evolution of the central zone of the zone are discussed. The. Sand River area is located in the northeast of the central zone of the Limbo wave belt in South Africa. A preliminary study of granulite facies rocks in the Sand River area of the Limbowave belt, South Africa, in terms of petrography, traditional geological thermometers, metamorphic facies balance, geochemistry and metamorphism can be obtained. The granulite is a type of island arc tholeiite and its metamorphic evolution can be divided into three different metamorphic stages: (1) peak period high-pressure metamorphic stage; (2) early retrograde metamorphic stage, (3) late retrograde metamorphic stage. The mineral assemblage of peak period (M1) is Grt Cpx Qtz Ilm Mag; early retrograde metamorphism (M2) mineral assemblage is Opx Pl 卤Grt 卤Cpx Qtz,; late retrograde metamorphism (M3) mineral assemblage is Amph Pl 卤Opx 卤Grt 卤Cpx Qtz,. The PTt trajectory of retrograde metamorphism is the process of clockwise near isothermal depressurization to cooling and lowering blood pressure. The temperature and pressure conditions of peak period (M1) metamorphism are estimated by traditional geological thermometers as TX 820-900 鈩，
本文编号：2410484
[Abstract]:The South African Limbowave belt is located between the Cape Walcraton and the Zimbabwe Craton. It is a world famous Archean to early Proterozoic tectonic event and high grade metamorphic tectonic belt. According to the characteristics of structure and rock assemblage, the limbo wave zone can be further divided into three zones: the northern marginal zone, the central zone and the southern marginal zone. The study of granulite facies in central zone, especially high-pressure granulite facies metamorphic rocks, has been widely concerned by scholars at home and abroad, especially the P-T locus of the central zone metamorphism and the structural evolution of the Limbowave zone. In this paper, the basic granulites in the Sand River region of the central zone of the South African Limbo Wave Zone are studied. The origin of basic granulites in the Sand River area of the central zone of the Limbo wave belt and the history of tectonic evolution of the central zone of the zone are discussed. The. Sand River area is located in the northeast of the central zone of the Limbo wave belt in South Africa. A preliminary study of granulite facies rocks in the Sand River area of the Limbowave belt, South Africa, in terms of petrography, traditional geological thermometers, metamorphic facies balance, geochemistry and metamorphism can be obtained. The granulite is a type of island arc tholeiite and its metamorphic evolution can be divided into three different metamorphic stages: (1) peak period high-pressure metamorphic stage; (2) early retrograde metamorphic stage, (3) late retrograde metamorphic stage. The mineral assemblage of peak period (M1) is Grt Cpx Qtz Ilm Mag; early retrograde metamorphism (M2) mineral assemblage is Opx Pl 卤Grt 卤Cpx Qtz,; late retrograde metamorphism (M3) mineral assemblage is Amph Pl 卤Opx 卤Grt 卤Cpx Qtz,. The PTt trajectory of retrograde metamorphism is the process of clockwise near isothermal depressurization to cooling and lowering blood pressure. The temperature and pressure conditions of peak period (M1) metamorphism are estimated by traditional geological thermometers as TX 820-900 鈩，
本文编号：2410484
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