研究生: |
楊雅淇 Ya-Chi Yang |
---|---|
論文名稱: |
喀麥隆喬立雷-班約剪切帶之板塊演化史 Tectonic evolution of Tcholliré-Banyo Shear Zone (TBSZ), Cameroon |
指導教授: |
李通藝
Lee, Tung-Yi 葉孟宛 Yeh, Meng-Wan |
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: | 2014 |
畢業學年度: | 102 |
語文別: | 英文 |
論文頁數: | 127 |
中文關鍵詞: | 鋯石鈾-鉛定年 、喬立雷-班約剪切帶 、板塊演化 、泛非洲 |
英文關鍵詞: | U-Pb Zircon Dating, Tcholliré-Banyo Shear Zone (TBSZ), Tectonic evolution, Pan-African |
論文種類: | 學術論文 |
相關次數: | 點閱:191 下載:11 |
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 |
位於喀麥隆境內的班約-喬立雷剪切帶 (Tcholliré-Banyo Shear Zone, TBSZ)是一個東北-西南走向的剪切帶,在喀麥隆屬於非洲中部剪切帶 (Central African Shear Zone, CASZ) 的分支。位處非洲三大地塊:西非古陸塊 (West African Craton)、剛果古陸塊 (Congo Craton)、與東撒拉古陸塊 (Eastern Sahara Block) 之交界處,其構造演化史可以完整記錄此區域相關板塊聚合與分離等板塊演化史。根據本研究於喀麥隆所採集之兩個片麻岩 (10CC02C、10CC05)、兩個糜稜岩(10CC03A、10CC03C) 與花崗岩 (10CC04) 之鋯石鈾-鉛定年結果顯示:主要年代集中於 1.8 ~ 2.1 Ga 與 696 ~ 514 Ma之間。而其鈾釷比值數據顯示:片麻岩 (10CC02C、10CC05)、糜稜岩 (10CC03A、10CC03C) 之核心鋯石 (1.85 ~ 2.14 Ga) 為火成鋯石 (Th/ U=0.12 ~ 1.23 > 0.1),但其外圍環帶 (696 ~ 514 Ma) 則為變質鋯石 (Th/ U=0.0013 ~ 0.0098 < 0.01),且其協和線之下交點約位於六億年前處。雖然花崗岩 (10CC04) 之鋯石鈾-鉛定年結果亦顯示相同之年代區間,但只有非常少的鋯石顯示較老的核心年代,大多數的鋯石顯示核心與周圍環帶記錄了相同之年代區間 (658 ~ 501 Ma)。除此之外,其鈾釷比值皆大於0.1 (Th/ U = 0.12 ~ 1.17) 顯示此花崗岩成岩於618 Ma ,而其較老之核心為繼承鋯石。
為釐清不同火成事件之板塊架構與其岩漿來源,本研究亦進行了全岩主要及微量元素分析與鋯石鉿同位素分析。除花崗岩之外,其他岩石樣本之微量元素皆遠低於正常火成岩之含量,這指出班約-喬立雷剪切帶內之片麻岩 (10CC02C、10CC05)、糜稜岩 (10CC03A、10CC03C) 之原岩為沈積岩。其沈積物質可能源自於伴隨古元古宙時期之埃伯尼造山運動 (Eburnean orogeny) 所形成之火成岩。雖其確切沈積事件之時間還無法確定,但可能與中元古宙時期形成的雅溫得統 (Yaoundé series) 及隆盆地 (Lom basins) 之年代相當。花崗岩樣本之鋯石鉿同位素 (εHf (T) values: -18.5 ~-11.2; +1.0 ~ +10.5) 顯示其岩漿包含地殼與地幔來源之混合訊號,因此可推測此伴隨東撒哈拉古陸塊 (Eastern Sahara Block)、西非古陸塊 (West African Craton) 與剛果古陸塊 (Congo Craton) 碰撞之泛非洲造山運動所形成之火成事件處於一弧陸碰撞之環境,且同時伴隨著角閃岩相之區域/接觸變質作用。根據岩石學之分析顯示此區域之變質沈積岩在泛非洲造山運動之後主要經歷了從角閃岩相變成綠片岩相之褪變質作用。鉀長石 (10CC02C) 之氬-氬定年結果顯示此區域之鉀長石由589 ~ 519 Ma持續受到班約-喬立雷剪切帶變形作用之影響。
關鍵字: 鋯石鈾-鉛定年、喬立雷-班約剪切帶、板塊演化、泛非洲
Tcholliré-Banyo Shear Zone (TBSZ), north Cameroon, is a NE-SW trending branch of the Central African Shear Zone (CASZ). The TBSZ situated within the boundaries of three major cratons: the Western African Craton, the Congo Craton, and the Eastern Sahara Block. By conducting geochronology, geochemistry and petrology analyses on ten samples coming from TBSZ and CASZ, this study attempt to decipher the tectonic evolution of this region. The U-Pb zircon ages of gneiss (10CC02C、10CC05), mylonite (10CC03A、10CC03C), and granite (10CC04) revealed two major age groups of (1.85 ~ 2.14 Ga) and (696 ~ 514 Ma). Except for the granite sample, the Th/ U (0.12 ~ 1.23) of the older core of all other samples are all larger than 0.1, which indicate a magmatic origin. The younger rim, however, showed Th/ U (0.0013 ~ 0.0098) < 0.01 indicating a metamorphic origin. The Th/ U are all larger than 0.1 for the granite sample indicating the granite crystallized during the 618 Ma (concordant age) Pan-African Orogeny, and the few older cores are inherited zircons.
In order to decipher the tectonic setting of the magmatic sources, whole rock XRF analysis of major and trace element with Hf isotope analysis of zircons are also conducted. Although the zircon U-Pb geochronology data of the Paleoproterozic core suggested a magmatic origin, the whole rock trace element distributions are far below the normal magmatic rocks. Which pointed out that the gneiss and mylonite samples are metasedimentary rocks, and the age in the core of zircons are inherited. Since the age in the core of zircons corresponds to the Paleoproterozoic magmatic event formed during the Eburnean orogeny by the collision between the South America and West Africa. This could be the source of sediments for these metasedimentary rocks. Although the sedimentary age was uncertain, it is possible that they have the same age as the Mesoproterozoic Yaoundé series in the Lom basins. The wide range of εHf (T) values (-18.5 ~ -11.2; +1.0 ~ +10.5) of the 618 Ma granite sample suggested the formation of this magmatic event is probably due to the Pan-African orogeny with collision between the Eastern Sahara Block with the Congo Craton and West African Craton under an arc environment. Other than magmatic event, the Pan-African orogeny also generated the regional metamorphism of surrounding metasedimentary rocks.
Petrological analysis of the metasedimentary rocks showed retrograde metamorphism from amphibolite facies to greenschist facies after the Pan-African event. 40Ar/39Ar dating of metamorphosed K-feldspar mineral separates of 10CC02C sample showed age ranges from 589 ~ 519 Ma indicating the deformation event of the TBSZ had occurred under the lower greenschist facies during this time.
Key Words:U-Pb Zircon Dating, Tcholliré-Banyo Shear Zone (TBSZ), Tectonic evolution, Pan-African
Abati, J., Aghzer, A. M., Gerdes, A., and Ennih, N., 2010, Detrital zircon ages of Neoproterozoic sequences of the Moroccan Anti-Atlas belt: Precambrian Research, v. 181, no. 1–4, p. 115-128.
Alkmim, F. F., Marshak, S., Pedrosa-Soares, A. C., Peres, G. G., Cruz, S. C. P., and Whittington, A., 2006, Kinematic evolution of the Araçuaí-West Congo orogen in Brazil and Africa: Nutcracker tectonics during the Neoproterozoic assembly of Gondwana: Precambrian Research, v. 149, no. 1–2, p. 43-64.
Baksi, A. K., Archibald, D., and Farrar, E., 1996, Intercalibration of 40Ar39Ar dating standards: Chemical geology, v. 129, no. 3, p. 307-324.
Barbarin, B., 1999, A review of the relationships between granitoid types, their origins and their geodynamic environments: Lithos, v. 46, no. 3, p. 605-626.
Bouyo Houketchang, M., Toteu, S. F., Deloule, E., Penaye, J., and Van Schmus, W. R., 2009, U-Pb and Sm-Nd dating of high-pressure granulites from Tcholliré and Banyo regions: Evidence for a Pan-African granulite facies metamorphism in north-central Cameroon: Journal of African Earth Sciences, v. 54, no. 5, p. 144-154.
Chiu, H.-Y., Chung, S.-L., Wu, F.-Y., Liu, D., Liang, Y.-H., Lin, I. J., Iizuka, Y., Xie, L.-W., Wang, Y., and Chu, M.-F., 2009, Zircon U–Pb and Hf isotopic constraints from eastern Transhimalayan batholiths on the precollisional magmatic and tectonic evolution in southern Tibet: Tectonophysics, v. 477, no. 1–2, p. 3-19.
England, P. C., and Thompson, A., 1986, Some thermal and tectonic models for crustal melting in continental collision zones: Geological Society, London, Special Publications, v. 19, no. 1, p. 83-94.
Eskola, P., 1915, On the relaiions between the chemical and mineralogical composition in ihe metamorphic rocks of the Orijarvi region: Bull. Comm. Geol. Finlande, v. 44, p. 109-143.
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, no. 2-4, p. 231-249.
Fairhead, J. D., Okereke, C. S., and Nnange, J. M., 1991, Crustal structure of the Mamfe basin, West Africa, based on gravity data: Tectonophysics, v. 186, no. 3-4, p. 351-358.
Forster, M., and Lister, G., 2004, The interpretation of 40Ar/39Ar apparent age spectra produced by mixing: application of the method of asymptotes and limits: Journal of Structural Geology, v. 26, no. 2, p. 287-305.
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, no. 8, p. 1405-1434.
Haskin, L., Wildeman, T., and Haskin, M., 1968, An accurate procedure for the determination of the rare earths by neutron activation: Journal of Radioanalytical and Nuclear Chemistry, v. 1, no. 4, p. 337-348.
Hawkesworth, C. J., and Kemp, A. I. S., 2006, Using hafnium and oxygen isotopes in zircons to unravel the record of crustal evolution: Chemical Geology, v. 226, no. 3–4, p. 144-162.
Hawthorne, F. C., KATO, A., KISCH, H. J., KRIVOVICHEV, V. G., LINTHOUT, K., LAIRD, J., MARESCH, W. V., SCHUMACHER, J. C., STEPHENSON, N. C., and WHITTAKER, E. J., 1997, Nomenclature of amphiboles: report of the subcommittee on amphiboles of the International Mineralogical Association, Commission on New Minerals and Mineral Names: The Canadian Mineralogist, v. 35, p. 219-246.
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, no. 1-2, p. 79-97.
Jackson, S. E., Pearson, N. J., Griffin, W. L., and Belousova, E. A., 2004, The application of laser ablation-inductively coupled plasma-mass spectrometry to in situ U–Pb zircon geochronology: Chemical Geology, v. 211, no. 1–2, p. 47-69.
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, no. 3-4, p. 258-272.
Kröner, A., and Stern, R., 2004, Africa: Pan-African orogeny: Encyclopedia of Geology. Elsevier, p. 1-12.
Lo, C.-H., Chung, S.-L., Lee, T.-Y., and Wu, G., 2002a, Age of the Emeishan flood magmatism and relations to Permian–Triassic boundary events: Earth and Planetary Science Letters, v. 198, no. 3–4, p. 449-458.
Lo, C.-H., Howard, K. T., Chung, S.-L., and Meffre, S., 2002b, Laser fusion argon-40/argon-39 ages of Darwin impact glass: Meteoritics & Planetary Science, v. 37, no. 11, p. 1555-1562.
Lo, C. H., and Lee, C. Y., 1994, 40Ar/39Ar Method of K-Ar Age Determination of Geological Samples Using Tsing-Hua Open-Pool (THOR) Reactor, p. 143-164.
Lu, Y. L., Liu, J. Q., Dou, L. R., Guo, Z. F., Xiao, K. Y., Hu, Y., and Du, Y. O., 2009, Geochemistry and petrogenesis of volcanic rocks from Chad basins, Africa: Acta Petrologica Sinica, v. 25, no. 1, p. 109-123.
Ludwig, K. R., 2003, User's Manual for Isoplot 3.00: A Geochronological Toolkit for Microsoft Excel, Kenneth R. Ludwig.
Middlemost, E. A. K., 1989, Iron oxidation ratios, norms and the classification of volcanic rocks: Chemical Geology, v. 77, no. 1, p. 19-26.
Moulin, M., Aslanian, D., and Unternehr, P., 2010, A new starting point for the South and Equatorial Atlantic Ocean: Earth-Science Reviews, v. 98, no. 1-2, p. 1-37.
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, no. 10, p. 1369-1383.
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, no. 3, p. 509-522.
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, no. 4-5, p. 494-510.
Njiekak, G., Dörr, W., Tchouankou, J.-P., and Zulauf, G., 2008a, 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, no. 3-4, p. 460-477.
Odin, G. S., CJ, A., RL, A., GP, B., AK, B., K, B., Barnes IL, Boelrijk NALM, Bonadonna FP, Bonhomme MG, Cassignol C, Chanin L, Gillot PY, Gledhill A, Govindaraju K, Harakal R, Harre W, Hebeda EH, Hunziker JC, Ingamells CO, Kawashita K, Kiss E, Kreutzer H, Long LE, McDougall I, McDowell F, Mehnert H, Montigny R, Pasteels P, Radicati F, Rex DC, Rundle CC, Savelli C, Sonet J, Welin E, and JL, Z., 1982, Interlaboratory standards for dating purposes: Numerical Dating in Stratigraphy, Wiley, New York, p. 123-149.
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, no. 4-5, p. 530-542.
Raase, P., 1974, Al and Ti contents of hornblende, indicators of pressure and temperature of regional metamorphism: Contributions to mineralogy and petrology, v. 45, no. 3, p. 231-236.
Renne, P. R., Swisher, C. C., Deino, A. L., Karner, D. B., Owens, T. L., and DePaolo, D. J., 1998, Intercalibration of standards, absolute ages and uncertainties in 40 Ar/39Ar dating: Chemical geology, v. 145, no. 1, p. 117-152.
Rogers, J. J. W., and Santosh, M., 2003, Supercontinents in Earth History: Gondwana Research, v. 6, no. 3, p. 357-368.
Rubatto, D., 2002, Zircon trace element geochemistry: partitioning with garnet and the link between U–Pb ages and metamorphism: Chemical Geology, v. 184, no. 1–2, p. 123-138.
Rubatto, D., and Gebauer, D., 2000, Use of Cathodoluminescence for U-Pb Zircon Dating by Ion Microprobe: Some Examples from the Western Alps, in Pagel, M., Barbin, V., Blanc, P., and Ohnenstetter, D., eds., Cathodoluminescence in Geosciences, Springer Berlin Heidelberg, p. 373-400.
Scherer, E. E., Whitehouse, M. J., and Münker, C., 2007, Zircon as a Monitor of Crustal Growth: Elements, v. 3, no. 1, p. 19-24.
Smith, W. H., and Sandwell, D. T., 1997, Global sea floor topography from satellite altimetry and ship depth soundings: Science, v. 277, no. 5334, p. 1956-1962.
Steiger, R. H., and Jäger, E., 1977, Subcommission on geochronology: convention on the use of decay constants in geo-and cosmochronology: Earth and planetary science letters, v. 36, no. 3, p. 359-362.
Sun, S.-S., and McDonough, W. F., 1989, Chemical and isotopic systematics of oceanic basalts: implications for mantle composition and processes: Geological Society, London, Special Publications, v. 42, no. 1, p. 313-345.
Tanko Njiosseu, E. L., Nzenti, J.-P., Njanko, T., Kapajika, B., and Nédélec, A., 2005, New UPb zircon ages from Tonga (Cameroon): coexisting Eburnean-Transamazonian (2.1 Ga) and Pan-African (0.6 Ga) imprints: Comptes Rendus Geosciences, v. 337, no. 6, p. 551-562.
Tchameni, R., Pouclet, A., Penaye, J., Ganwa, A. A., and Toteu, S. F., 2006, Petrography and geochemistry of the Ngaoundéré Pan-African granitoids in Central North Cameroon: Implications for their sources and geological setting: Journal of African Earth Sciences, v. 44, no. 4-5, p. 511-529.
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, no. 1, p. 73-85.
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, no. 1-2, p. 45-73.
Windley, B. F., 1984, The evolving continents: Chichester, England and New York, John Wiley and Sons, 1984, 416 p., v. 1.
Winter, J. D., 2001, An introduction to igneous and metamorphic petrology, Prentice Hall New Jersey.
Wu, F.-Y., Yang, Y.-H., Xie, L.-W., Yang, J.-H., and Xu, P., 2006, Hf isotopic compositions of the standard zircons and baddeleyites used in U–Pb geochronology: Chemical Geology, v. 234, no. 1–2, p. 105-126.
Wu, S. M., 2012, Petrographic Analysis and Structural History of Central African Shear Zone [Master: National Normal Taiwan University.
Zhao, G., Cawood, P. A., Wilde, S. A., and Sun, M., 2002a, Review of global 2.1-1.8 Ga orogens: implications for a pre-Rodinia supercontinent: Earth-Science Reviews, v. 59, no. 1-4, p. 125-162.
Zhao, G., Sun, M., and Wilde, S. A., 2002b, Did South America and West Africa Marry and Divorce or Was it a Long-lasting Relationship?: Gondwana Research, v. 5, no. 3, p. 591-596.