CAJ | 학술논문

滇西地区特提斯造山带具有多块体拼合的构造特点,是东特提斯造山带的重要组成部分之一,其大地构造演化对理解全球特提斯造山带具有重要的地质意义.在腾冲和保山地块之间的龙陵-瑞丽断裂带中出露超镁铁质岩石,曾被解释为两个陆块缝合的证据.本文采用高灵敏度高精度超低本底Re-Os、Sm-Nd、Pb和Rb-Sr同位素分析技术,对采自该断裂带潞西三台山的超镁铁岩样品进行了Os-Nd-Pb-Sr同位素测定.分析结果表明,这些超镁铁岩石具有强烈富集特征.分析的5个岩石样品具有高的初始~(87)Sr/~(86)Sr值(0.71074～0.71444)、低的初始ε_(Nd)值(-6.2～-10.6)、低初始γ_(Os)值(-4.8～-8.8)和较高的初始铅同位素比值,其Os同位素模式年龄值(t_(RD))为0.97～1.71Ga.Nd-Os同位素组成特征表明,三台山超镁铁岩具有古老的富集大陆岩石圈地幔岩石的特征,不能作为腾冲和保山地块的缝合证据.
전서지구특제사조산대구유다괴체병합적구조특점,시동특제사조산대적중요조성부분지일,기대지구조연화대리해전구특제사조산대구유중요적지질의의.재등충화보산지괴지간적룡릉-서려단렬대중출로초미철질암석,증피해석위량개륙괴봉합적증거.본문채용고령민도고정도초저본저Re-Os、Sm-Nd、Pb화Rb-Sr동위소분석기술,대채자해단렬대로서삼태산적초미철암양품진행료Os-Nd-Pb-Sr동위소측정.분석결과표명,저사초미철암석구유강렬부집특정.분석적5개암석양품구유고적초시~(87)Sr/~(86)Sr치(0.71074～0.71444)、저적초시ε_(Nd)치(-6.2～-10.6)、저초시γ_(Os)치(-4.8～-8.8)화교고적초시연동위소비치,기Os동위소모식년령치(t_(RD))위0.97～1.71Ga.Nd-Os동위소조성특정표명,삼태산초미철암구유고로적부집대륙암석권지만암석적특정,불능작위등충화보산지괴적봉합증거.
The western Yunnan Tethyan terrain that is formed by the amalgamation of multiple continental blocks represents an important part of the eastern Tethyan tectonic belt. Its tectonic evolution bears essential significances for understanding the formation of the global Tethyan orogenic belt. Along the Longling-Ruili fault zone between the Tengchong and Baoshan blocks, many small outcrops of ultramafic rocks are exposed, which have ever been interpreted as evidence for the suturing of these two blocks. Os-Nd-Pb-Sr isotopic compositions of ultramafic rocks sampled from Santaishan massif were analyzed by using low procedural blank and high precision analytical techniques in this study. Analytical results show that these ultrmafic rocks exhibit isotopic characteristics of strong enrichment. Five analyzed samples of ultramafic rock yield high initial ~(87)Sr/~(86)Sr values (0.71074 ～0.71444), low initial ε_(Nd) values (-6.2 ～ -10.6), low initial γ_(Os) values (-4.8 ～ -8.8) and relative high initial Pb isotopic ratios. Os isotopic model ages (t_RD)) range from 0.97 to 1.71Ga. The Nd-Os isotopic compositions indicate that the Santaishan ultramafic rocks are characterized by theisotopic feature of old sub-continental lithospheric mantle and therefore, can not represent evidence for a suture between the Tengchong and Baoshan blocks.