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題 名 | 40Ar/39Ar Thermochronology of Granitoids from the Pingtan-Dongshan Metamorphic Belt and Its Tectonic Implications=平潭-東山變質帶花崗質岩之氬-氬年代學研究及其大地構造演化之意義 |
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作 者 | 楊小青; 陳文山; 羅清華; 陳正宏; 黃輝; 汪新; 王執明; | 書刊名 | 中國地質學會會刊 |
卷 期 | 40:3 1997.07[民86.07] |
頁 次 | 頁559-585 |
分類號 | 358.43 |
關鍵詞 | 氬-氬同位素定年; 變質作用; 福建; 40Ar/39Ar geochronology; Metamorphism; Fujian; |
語 文 | 英文(English) |
中文摘要 | 平潭東山變質帶為歐亞大陸東南緣一條重要的變質帶,長久以來吸引眾 多的地質工作者的注意。本研究工作利用氬-氬定年學方法,分析了晉江半 島片麻狀混合岩、黑雲母花崗岩、細晶岩及基性岩脈之角閃石、黑雲母、鉀 長石及全岩之氬同位素成份。氬氬定年結果顯示,在晉江半島之長樂-南澳 斷裂帶約於一億二百萬年前活動,同時造成變質岩快速抬升,初期冷卻速率 高達173度/百萬年,其後之冷卻速率降至~12度/百萬年,而在八千萬年 之後冷卻速率更進一步降低為2~3度/百萬年。 在平潭東山變質帶抬升的同時,長樂-南澳斷裂帶的兩側均有所謂的I型 與A型花崗岩侵入,隨後又見大量基性岩脈侵入於花崗岩與變質岩中。此種 現象配合福建省境內其他地質資料,顯示了中生代晚期本變質帶的區域抬升 與岩漿的侵入,並非如前人所言直接導因於板塊聚合的壓縮作用,毋寧板塊 內部的舒張作用提供了更直接的營力機制。 |
英文摘要 | As one of major metamorphic belts along the southeastern margin of the Asian plate, the Pingtan-Dongshan Metamorphic Belt, Fujian Province, has attracted much of geoscientists' attention for the past few years, since it records the Mesozoic tectonic evolution of SE Asia. □Ar/□Ar dating of migmatitic gneisses yields Cretaceous ages for minerals extracted from granitoids and dyke rocks from the Metamorphic Belt in Jinjiang Peninsula. It is also shown that the cooling rate of these metamorphic rocks was very fast at beginning, at about 173℃/m.y., followed by a slower rate at about 12℃/m.y., and then declined to 2~3℃/m.y. after 80 Ma. Assuming that uplift rate is a function of cooling rate, it is then interesting to note that fast uplifting occurred simultaneously with intrusions of granites (I- and A-type) and diorites at about 100 Ma, and the whole terrane was subsequently intruded by a number of mafic dykes at a later stage (~82 Ma). Considering together with other geological evidences, these results strongly indicate that the exhumation of the metamorphic rocks and the magmatic activities in this Belt seem to have resulted from a late Mesozoic transtensional tectonic, rather than directly from a subduction/collision or subduction tectonics as has been previously advocated by many authors. |
本系統中英文摘要資訊取自各篇刊載內容。