研究生: |
林治蔚 Lin Chih-Wei |
---|---|
論文名稱: |
海洋鑽探計劃187航次玄武岩之實驗岩石學研究 |
指導教授: | 劉德慶 |
學位類別: |
碩士 Master |
系所名稱: |
地球科學系 Department of Earth Sciences |
論文出版年: | 2002 |
畢業學年度: | 90 |
語文別: | 中文 |
論文頁數: | 69 |
中文關鍵詞: | 海洋鑽探計劃 、中洋脊玄武岩 、實驗岩石學 |
英文關鍵詞: | AAD |
論文種類: | 學術論文 |
相關次數: | 點閱:237 下載:9 |
分享至: |
查詢本校圖書館目錄 查詢臺灣博碩士論文知識加值系統 勘誤回報 |
摘 要
本研究所使用的岩石樣本,為海洋鑽探計劃第187航次於東南印度洋脊附近所鑽獲的海洋地殼玄武岩,其主要組成礦物為斜長石及橄欖石,結晶顆粒小,無斑狀組織,屬無斑隱晶質玄武岩。
本研究的目的在模擬自然界岩漿所在的環境,來了解此玄武岩質岩漿在不同壓力下的結晶溫度及結晶次序,更進一步探討其岩漿演化的機制及過程,推論此岩石的生成環境。
根據實驗結果,其一大氣壓下的全熔溫度約為1269℃,固相線溫度稍低於1169℃。結晶次序為:氧化物、斜長石、斜輝石及橄欖石、直輝石(橄欖石消失)。斜長石的An值,隨溫度的下降有降低的趨勢;各溫度晶出之斜輝石成分則變化不大;氧化物則隨溫度下降鐵、鈦的含量上升,鉻、鎂則下降。1.0京帕下的全熔溫度約為1280℃,固相線溫度低於1160℃。結晶次序為:斜長石及斜輝石、直輝石、鈦鐵氧化物。
在玄武岩四面體的分類中,原岩屬橄欖石矽質玄武岩,殘餘岩漿有向石英矽質玄武岩演化的趨勢。一大氣壓下,隨著溫度下降玻璃成分之矽含量上升;鋁、鈣及鎂則下降;Na2O/TiO2與MgO值,皆隨溫度下降而降低,以此而言,太平洋型中洋脊玄武岩,並不會經過結晶分化而演變成印度洋型。在AFM圖中,岩漿初始成分在矽質玄武岩範圍內,演化初期朝全量鐵富集,之後向鹼金屬富集。
根據實驗結果,殘餘岩漿成分有朝向石英富集的趨勢,一大氣壓及1.0京帕下礦物晶出的順序和前人研究相符。和原岩中的礦物相比較後,顯示此玄武岩應該是在1.0京帕及一大氣壓之間,較接近一大氣壓的低壓環境下生成,生成深度小於30公里。
本研究之中洋脊玄武岩形成過程為,在上升的過程中經過些微結晶分化,隨著岩漿的上升、溫度的下降,在橄欖石晶出之後,因接近海床面而急速冷卻,所以形成主要礦物為斜長石及橄欖石的玄武岩。
參考文獻
Bowen, N. L. 1913. The melting phenomena of the plagioclase feldspars. Am. Jour. Sci. 35: 577-599.
Christie, D. M., B. P. West, D. G. Pyle and B. Hanan. 1998. Chaotic topography, mantle flow and mantle migration in the Australian-Antarctic Discordance. Nature 394: 637-644.
Christie, D. M., R. B. Pederson, D. J. Miller and shipboard scientific party. 2001. Proc. Ocean Drilling Program, Initial Reports, 187. College Station, TX.
Christie, D. M., R. B. Pederson, D. J. Miller, V. G. Balzer, F. Einaudi, M.A. M. Gee, F. Hauff, P. D. Kempton, W.T. Liang, K. Lysnes, C. M. Meyzen, D. G. Pyle, C. J. Russo, H. Sato and I. H. Thorseth (Shipboard Scientific Party). 2000. Preliminary Summary of Drilling Results, Ocean Drilling Program, Leg 187. 1.
Elthon, D. and C. M. Scarfe. 1984. High-pressure phase equilibria of a high-magnesia basalt and the genesis of primary oceanic basalts. American Mineralogist 69: 1-15.
Ford, C. E. 1978. Platinum-iron alloy sample containers for melting experiments on iron-bearing rocks, minerals, and relates systems. Mineralogical Magazine 42: 271-275.
Grove, T. L. and M. B. Baker 1984. Phase equlibrium controls on the tholeiitic versus calc-alkaline differentiation trends. Journal of Geophysical research 89: 3253-3274.
Grove, T. L. and W. B. Bryan. 1983. Fractionation of pyroxene-phyric MORB at low pressure: an experimental study. Contrib. Min. Pet. 84: 293-309.
IGPET99(soft ware). 1999. Terra Softa Inc.
Klein, E. M., C. H. Langmuir, A. Zindler, H. Staudigel and B. Hamelin. 1988. Isotope evidence of a mantle convection boundary at the Australian-Antarctic discordance. Nature 333: 623-629.
Kawamoto, T. and K. Hirose. 1994. Au-Pd sample containers for melting experiments on iron and water bearing systems. Eur. J. Mineral. 6: 381-385.
Kuno, H. 1965. Fractionation trends of basalt magmas in lava flows. J. Petrol. 6: 302-321.
Lanyon, R., A. J. Crawford and S. Eggins. 1995. Westward migration of Pacific Ocean upper mantle into the Southern Ocean region between Australia and Antarctica. Geology 23: 511-514.
Liu, T. C. and D. C. Presnall. 1990. Liquidus phase relationships on the join anorthite-forsterite-quartz at 20 kbar with applications to basalt petrogenesis and igneous sapphirine. Contrib. Mineral. Petrol. 104: 735-742.
McBirney, A. R. and H. Williams. 1969. Geology and petrology of Galapagos Island. Mem. Geol. Soc. Am. 118: 197
O'Donnell, T. H. and D. C. Presnall. 1980. Chemical variations of the glass and mineral phases in basalts dredged from 25°-30° N along the Mid-Atlantic Ridge. Am. J. Sci. 280-A: 845-868.
Presnall, D. C. 1999. Effect of pressure on the fractional crystallization of basaltic magma. The Geochemical Society, Special Publication 6: 209-224.
Presnall, D. C. and J. D. Hoover. 1984. Composition and depth of origin of promary mid-ocean ridge basalts. Contrib. Mineral. Petrol. 87: 170-178.
Pyle, D. G., D. M. Christie and J. J. Mahoney. 1990. Upper mantle flow in the Australian-Antarctic Discordance. EOS 71: 1388.(Abstract)
Pyle, D. G., D. M. Christie and J. J. Mahoney. 1992. Resolving an isotopic boundary within the Australian-Antarctic Discordance. Earth Planet. Sci. Lett. 112: 161-178.
Pyle, D. G., D. M. Christie, J. J. Mahoney and R. A. Dancan. 1995. Geochemistry and geochronology of ancient southeast Indian and southwest Pacific seafloor. J. Geophys. Res. 100: 22: 261-282.
Sack, R. C., D. Walker and I. S. E. Carmichael. 1987. Experimental petrology of alkalic lavas: constraints on cotectics of multiple saturation in natural basic liquids. Contrib. Mineral. Petrol. 96: 1-23.
Stolper, E. 1980. A phase Diagram for Mid-Ocean Ridge Basalts: Preliminary Results and Implications for Petrogenesis. Contirb. Mineral. Petrol. 74: 13-27.
Tormey, D. R., T. L. Grove and W. B. Bryan. 1987. Experimental petrology of normal MORB near the Kane Fracture Zone: 22°-25°N, Mid-Atlantic ridge. Contrib. Mineral. Petrol. 96: 121-139.
Yoder, H. S. J. and C. E. Tilley. 1962. Origin of basalt magmas: an experimental study of natural and synthetic rock systems. J. Petrol. 3: 342-532.