https://scholars.lib.ntu.edu.tw/handle/123456789/37180
標題: | 東亞地體構造演化整合研究計畫(I)─(總計畫及子計畫三)紅河-哀牢山斷裂帶附近地區熱事件及地塊運動研究(III) | 其他標題: | Cenozoic Thermal Events and Block Movements along the Ailaoshan – Red River Fault Zone (III) | 作者: | 羅清華 | 關鍵字: | 西藏高原;熱定年學;eastern Tibet;U-Pb dating;39 Ar-40 Ar dating;thermochronolog | 公開日期: | 2000 | 出版社: | 臺北市:國立臺灣大學地質科學系暨研究所 | 摘要: | 本研究計畫工作利用40 Ar/39 Ar 與U-Pb 定年法 研究哀牢山-紅河斷裂帶南緣之基盤花崗岩-Posen Complex 之熱歷史、U-Pb 定年結果顯示、該花崗岩 體可能形成於晚原生代(885±96 Ma )、但在早古 生代時期(490±66Ma)曾受強烈的變質作用。相對 地,礦物40 Ar/39 Ar 年代則顯得年輕,均顯示早第三 紀之年代(40-30Ma),標誌著抬升冷卻之年代,此 一抬升時間似早於哀牢山-紅河斷裂帶之年紀(27-17Ma) 。如考慮哀牢山-紅河斷裂帶之左移距離與 年代,於早第三紀時期,此一花崗岩體應位於西藏 高原之東緣,果真如此,則上述之早第三紀之抬升 年代應可視為記錄著西藏高原早期抬升之證據。 Paleogene southeastward extrusion of the Indochinese block with respect to the South China block transported some basement complexes from eastern Tibet to northern Vietnam in accommodating the India-Asian continental collision. One of those transported basement complexes, the Posen complex in northern Vietnam, was studied thermochronologically by U-Pb and 40 Ar/39 Ar methods. Zircon U-Pb dating yields an upper intercept date of 885 ± 96 Ma, corresponding to the emplacement age of the protolith and a lower intercept age of 490 ± 66 Ma, which may indicate a thermal event in early Paleozoic age. 40 Ar/39 Ar results for micas and K-feldspars in the range of 30 to 36 Ma suggest a rapid cooling and exhumation history of the Posen complex during the Paleogene. The time span for exhumation/cooling recorded in the Posen complex is surprisingly coincident with the earlier stage of the rapid uplifting (40 to 30 Ma) in the eastern Tibetan plateau, but clearly older than the age range for the left-lateral shearing of the Ailao Shan-Red River (ASRR) shear zone (27-17 Ma). Given the fact that the Indochinese block was once attached to eastern Tibet in SW China prior to the extrusion, the present results would not only be a good constraint for the early rapid uplifting of the eastern Tibet during the Paleogene, but also provide an independent evidence for the initiation for the left-lateral movement along the ASRR shear zone. |
URI: | http://ntur.lib.ntu.edu.tw//handle/246246/11750 | 其他識別: | 892116M002017 | Rights: | 國立臺灣大學地質科學系暨研究所 |
顯示於: | 地質科學系 |
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892116M002017.pdf | 71.87 kB | Adobe PDF | 檢視/開啟 |
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