Title

非洲中部剪切帶岩石學分析與構造史之研究

Translated Titles

Petrographic Analysis and Structural History of Central African Shear Zone

Authors

吳詩敏

Key Words

非洲中部剪切帶 ; 泛非洲 ; 顯微構造 ; 應變分析 ; 岩石學 ; Rf/φ分析法 ; 應變橢球 ; 福林氏圖 ; Central African Shear Zone ; Pan-African ; microstructure ; strain analysis ; petrography ; Rf/φ method ; strain ellipsoid ; Flinn diagram

PublicationName

臺灣師範大學地球科學系學位論文

Volume or Term/Year and Month of Publication

2012年

Academic Degree Category

碩士

Advisor

李通藝;葉孟宛

Content Language

繁體中文

Chinese Abstract

非洲中部剪切帶 (Central African Shear Zone,CASZ) 為一東北-西南走向從喀麥隆至查德向東北延伸至蘇丹之剪切帶,於喀麥隆地區分為北偏東70 度之中喀麥隆剪切帶 (Central Cameroon Shear Zone,CCSZ) 與北偏東50 度之 Tcholliré-Banyo 剪切帶(Tcholliré-Banyo Shear Zone,TBSZ),且在大陸漂移前延伸至巴西東北部。而板塊構造背景可追溯至泛非洲時期,剛果地塊、西非地塊及東撒哈拉地塊之拼合。部分學者提出CASZ 有同構造之花岡岩侵入,並以鈾-鉛鋯石定年640 至557 Ma 之結果為花崗岩與剪切帶形成之時間;另一部分研究則以沿CASZ 有裂谷盆地分布與其打開的時間為大西洋張裂之時,進而探討130 Ma 至84Ma 之板塊構造演化,認為CASZ 之形成與大西洋張裂相關,而同剪切花崗岩中常含有高溫變質岩,因此本研究於TBSZ 系統以顯微岩石學之分析來了解其礦物相,並以指標礦物 推測其變質事件發生之溫度條件;並根據野外觀察、顯微構造及應變分析釐清整個構造演化歷史及應力分布情況,歸納此地區的變形史可分為至少三期:早期的為Dn-1,形成一東北-西南走向,低角度向東南傾之偃臥褶皺,葉理Sn-1 組成礦物為角閃石+黑雲母+石榴子石+鈉長石,此礦物相為角閃岩相之變質條件,而Dn-1 應為泛非洲時期東撒哈拉地塊由北向南碰撞變形造成之逆衝nappe;Dn 形成東北-西南走向,近垂直傾向西北走向平行剪切帶之直立褶皺,顯微影像與電子影像分析顯示Sn 葉理礦物相為黑雲母+綠泥石+鉀長石+榍石,此礦物成分指出溫壓條件為綠色片岩相,而此變形期為CASZ 左移剪切的時期,由重建應變橢球顯示主應力方向在北北西-南南東至西北-東南向,應 變模式為左移伸張;Dn+1 為脆性變形事件,發生於接近地表的低溫條件。

English Abstract

The N70˚E trending Central Cameroon shear zone (CCSZ) and the N50˚E trending Tcholliré-Banyo Shear zone (TBSZ) are the southwest extension of the Central African Shear Zone (CASZ). The evolution of CASZ is interpreted in two different models. The activation of the CASZ was considered to relate to the evolution of the Western Gondwana. Many researchers proposed the emplacement of these plutons are syn-kinematic, with U-Pb zircon ages of 640-580 Ma for various shear zone parallel batholith. The activation of the CASZ is due to amalgamation of the Congo craton to the West Africa craton and the Eastern Saharan Block. However, there are many rift basins along CASZ. The formations of these rift systems are associated with the opening of Atlantic Ocean. CASZ can also be activated or reactivated due to the opening of the southern Atlantic Ocean during 130-84 Ma. There are existences of high-temperature metamorphic rocks due to shearing heating in syn-shearing granite. In order to understand the metamorphic conditions, micropetrography helps to indicate the mineral assemblage and, which helps to delineate the temperature comdition of metamorphism. With new field observation, microstructural data and strain analysis, the tectonic history of TBSZ can be devided into at least three events. The earlier event Dn-1 formed recumbent folds with NE-SW striking, SE dipping fold axial planes. The mineral assemblage of Sn-1 is hornblend ± garnet ± biotite ± Albite suggested that P-T conditions in under middle Amphibolite facies. Dn-1 is result from the amalgamation of the Congo craton and the Eastern Saharan Block in N-S direction by the analysis of structure and strain. Dn event formed tight upright folds with NE-SW striking subvertical axial planes and parallel to CASZ. Sn with mineral assemblage Biotite ± Chlorite ± Sphene ± K-feldspar form under greenschist facies and left-lateral shearing. By reconstruction of strain ellipsoids, the main stress direction is NNW-SSE to NW-SE during Dn with transtension strain pattern . Dn+1 is brittle deformation close to surface by low temperature.

Topic Category 基礎與應用科學 > 地球科學與地質學
理學院 > 地球科學系
Reference
  1. Attoh, K., Dallmeyer, R.D., and Affaton, P., 1997, Chronology of nappe assembly in the Pan-African Dahomeyide orogen, West Africa: evidence from 40Ar39Ar mineral ages: Precambrian Research, v. 82, p. 153-171.
    連結:
  2. Bertrand, J.M., and Jardim de Sà, E.F., 1990, Where are the Eburnean-Transamazonian collisional belts?: Canadian Journal of Earth Sciences, v. 27, p. 1382-1393.
    連結:
  3. Bessoles, B., and Trompette, R., 1980, Géologie de l'Afrique. La chaîne panafricaine: "zone mobile d'Afrique Centrale (partie sud) et zone mobile soudanaise": Mémoire du B.R.G.M., France, v. 92, p. 396.
    連結:
  4. Binks, R.M., and Fairhead, J.D., 1992, A plate tectonic setting for Mesozoic rifts of West and Central Africa: Tectonophysics, v. 213, p. 141-151.
    連結:
  5. Castaing, C., Feybesse, J.L., Thiéblemont, D., Triboulet, C., and Chèvremont, P., 1994, Palaeogeographical reconstructions of the Pan-African/Brasiliano orogen: closure of an oceanic domain or intracontinental convergence between major blocks?: Precambrian Research, v. 69, p. 327-344.
    連結:
  6. David, M.C., 2003, An Excel spreadsheet for finite strain analysis using the Rf/φ technique: Computers & Geosciences, v. 29, p. 795-799.
    連結:
  7. Davison, I., McCarthy, M., Powell, D., Torres, H.H.F., and Santos, C.A., 1995, Laminar flow in shear zones: the Pernambuco Shear Zone, NE-Brazil: Journal of Structural Geology, v. 17, p. 149-161.
    連結:
  8. Fairhead, J.D., 1988, Mesozoic plate tectonic reconstructions of the central South Atlantic Ocean: The role of the West and Central African rift system: Tectonophysics, v. 155, p. 181-191.
    連結:
  9. Fairhead, J.D., and Binks, R.M., 1991, Differential opening of the Central and South Atlantic Oceans and the opening of the West African rift system: Tectonophysics, v. 187, p. 191-203.
    連結:
  10. Fairhead, J.D., and Green, C.M., 1989, Controls on rifting in Africa and the regional tectonic model for the Nigeria and East Niger rift basins: Journal of African Earth Sciences, v. 8, p. 231-249.
    連結:
  11. Flinn, D., 1962, On folding during three-dimensional progressive deformation: Geological Society of London Quarterly Journal, v. 118, p. 385-433.
    連結:
  12. Genik, G.J., 1993, Petroleum geology of Cretaceous-Tertiary rift basins in Niger, Chad, and Central African Republic American Association of Petroleum Geologists Bulletin, v. 77, p. 1405-1434.
    連結:
  13. Ibrahim, A.E., Ebinger, C.J., and Fairhead, J.D., 1996, Lithospheric extension northwest of the Central African Shear Zone in Sudan from potential field studies: Tectonophysics, v. 255, p. 79-97.
    連結:
  14. Kankeu, B., Greiling, R.O., and Nzenti, J.P., 2009, Pan-African strike-slip tectonics in eastern Cameroon-Magnetic fabrics (AMS) and structure in the Lom basin and its gneissic basement: Precambrian Research, v. 174, p. 258-272.
    連結:
  15. Lisle, R.J., 1977, Clastic grain shape and orientation in relation to cleavage from the Aberystwyth Grits, Wales: Tectonophysics, v. 39, p. 381-395.
    連結:
  16. Marzoli, A., Piccirillo, E.M., Renne, P.R., Bellieni, G., Iacumin, M., Nyobe, J.B., and Tongwa, A.T., 2000, The Cameroon Volcanic Line Revisited: Petrogenesis of Continental Basaltic Magmas from Lithospheric and Asthenospheric Mantle Sources: Journal of Petrology, v. 41, p. 87-109.
    連結:
  17. Maurin, J.C., and Guiraud, R., 1993, Basement control in the development of the early cretaceous West and Central African rift system: Tectonophysics, v. 228, p. 81-95.
    連結:
  18. Mookerjee, M., and Nickleach, S., 2011, Three-dimensional strain analysis using Mathematica: Journal of Structural Geology, v. 33, p. 1467-1476.
    連結:
  19. Moulin, M., Aslanian, D., and Unternehr, P., 2010, A new starting point for the South and Equatorial Atlantic Ocean: Earth-Science Reviews, v. 98, p. 1-37.
    連結:
  20. Neves, S.P., and Mariano, G., 1999, Assessing the tectonic significance of a large-scale transcurrent shear zone system: the Pernambuco lineament, northeastern Brazil: Journal of Structural Geology, v. 21, p. 1369-1383.
    連結:
  21. Neves, S.P., Melo, S.C., Moura, C.A.V., Mariano, G., and Rangel Da Silva, J.M., 2004, Zircon Pb-Pb Geochronology of the Caruaru Area, Northeastern Brazil: Temporal Constraints on the Proterozoic Evolution of Borborema Province: International Geology Review, v. 46, p. 52-63.
    連結:
  22. Ngako, V., Affaton, P., and Njonfang, E., 2008, Pan-African tectonics in northwestern Cameroon: Implication for the history of western Gondwana: Gondwana Research, v. 14, p. 509-522.
    連結:
  23. Njanko, T., Nédélec, A., and Affaton, P., 2006, Synkinematic high-K calc-alkaline plutons associated with the Pan-African Central Cameroon shear zone (W-Tibati area): Petrology and geodynamic significance: Journal of African Earth Sciences, v. 44, p. 494-510.
    連結:
  24. Njiekak, G., Dorr, W., Tchouankou, J.-P., and Zulauf, G., 2008, U-Pb zircon and microfabric data of (meta) granitoids of western Cameroon: Constraints on the timing of pluton emplacement and deformation in the Pan-African belt of central Africa: Lithos, v. 102, p. 460-477.
    連結:
  25. Nkouathio, D., Kagou Dongmo, A., Bardintzeff, J., Wandji, P., Bellon, H., and Pouclet, A., 2008, Evolution of volcanism in graben and horst structures along the Cenozoic Cameroon Line (Africa): implications for tectonic evolution and mantle source composition: Mineralogy and Petrology, v. 94, p. 287-303.
    連結:
  26. Penaye, J., Kröner, A., Toteu, S.F., Van Schmus, W.R., and Doumnang, J.-C., 2006, Evolution of the Mayo Kebbi region as revealed by zircon dating: An early (ca. 740 Ma) Pan-African magmatic arc in southwestern Chad: Journal of African Earth Sciences, v. 44, p. 530-542.
    連結:
  27. Ramsay, J.G., 1967b, A re-interpretation of the mechanics of the ben sgriol fold, loch hourn (northwest scotland): A reply: Tectonophysics, v. 5, p. 63-67.
    連結:
  28. Sandwell, D.T., and Smith, W.H.F., 1997, Marine gravity anomaly from geosat and ERS 1 satellite altimetry: Journal of Geophysical Research, v. 102, p. 10039-10054.
    連結:
  29. Searle, M.P., 2006, Role of the Red River Shear zone, Yunnan and Vietnam, in the continental extrusion of SE Asia: Journal of the Geological Society, v. 163, p. 1025-1036.
    連結:
  30. Torsvik, T.H., and Cocks, L.R.M., 2011, The Palaeozoic palaeogeography of central Gondwana: Geological Society, London, Special Publications, v. 357, p. 137-166.
    連結:
  31. Toteu, S.F., 1990, Geochemical characterization of the main petrographical and structural units of Northern Cameroon: implications for Pan-African evolution: Journal of African Earth Sciences (and the Middle East), v. 10, p. 615-624.
    連結:
  32. Toteu, S.F., Fouateu, R.Y., Penaye, J., Tchakounte, J., Mouangue, A.C.S., Van Schmus, W.R., Deloule, E., and Stendal, H., 2006, U-Pb dating of plutonic rocks involved in the nappe tectonic in southern Cameroon: consequence for the Pan-African orogenic evolution of the central African fold belt: Journal of African Earth Sciences, v. 44, p. 479-493.
    連結:
  33. Toteu, S.F., Penaye, J., and Djomani, Y.P., 2004, Geodynamic evolution of the Pan-African belt in central Africa with special reference to Cameroon: Canadian Journal of Earth Sciences, v. 41, p. 73-85.
    連結:
  34. Toteu, S.F., Van Schmus, W.R., Penaye, J., and Michard, A., 2001, New U-Pb and Sm-Nd data from north-central Cameroon and its bearing on the pre-Pan African history of central Africa: Precambrian Research, v. 108, p. 45-73.
    連結:
  35. Lu, Y.L., Liu, J.Q., Dou, L.R., Guo, Z.F., Xiao, K.Y., Hu, Y., Du, Y.B., and Meng, F.C., 2009, K-Ar and 39Ar-40Ar geochronology of basalts from the Chad Basins, Africa and its geodynamics setting: Acta Geological Sinica, v. 83, p. 1125-1133.
  36. Nédelec, A, Macaudiére, J, Nzenti, J, P., Barbey, and P, G., 1986, Evolution structurale et métamorphique des schistes de Mbalmayo (Cameroun). Implications pour la structure de la zone mobile pan-africaine d'Afrique centrale, au contact du craton du Congo, Volume 303: Comptes rendus de l'Académie des sciences. Série II. Mécanique, physique, chimie, sciences de l'univers, sciences de la terre: Paris, FRANCE, Gauthier-Villars.
  37. Ramsay, J.G., 1967a, Folding and fracturing of rocks: McGrqw-Hill Book Company: New York.
  38. Zingg, T., 1935, Beitrag zur Schotteranalyze: Schweizer Mineralogische und Petrographische Mitteilungen, v. 15, p. 39-140.