西藏罗布莎豆荚状铬铁矿中发现超高压矿物柯石英

杨经绥; 白文吉; 方青松; 颜秉刚; 戎合; 陈松永

西藏罗布莎豆荚状铬铁矿中发现超高压矿物柯石英

中国地质科学院地质研究所部大陆动力学重点实验室, 北京 100037

基金项目:

地质调查项目 200313000058

国家“973”专项项目 2003CB716500

详细信息

作者简介:
杨经绥(1950-), 男, 留加博士, 研究员, 主要从事青藏高原和造山带的蛇绿岩、火山岩和超高压变质岩研究, 侧重于岩石-构造学的研究

中图分类号: P589
计量
- 文章访问数: 3642
- HTML全文浏览量: 66
- PDF下载量: 4
- 被引次数: 0
出版历程
- 收稿日期: 2004-09-07
- 刊出日期: 2004-11-25

Coesite Discovered from the Podiform Chromitite in the Luobusha Ophiolite, Tibet

摘要

摘要: 在西藏雅鲁藏布江蛇绿岩带东段的罗布莎豆荚状铬铁矿床中发现典型的超高压矿物柯石英和蓝晶石, 二者呈针柱状交生, 产在一个以TiFe合金成分为主的颗粒(0.7mm× 0.5mm大小) 的最外部.该颗粒从内到外由4层矿物组成, 分别为TiFe合金主体、2 0~ 70 μm宽的自然钛、约10 μm宽的TiSi合金及30~ 5 0 μm宽的柯石英和蓝晶石为主的硅酸岩和氧化物层.主体矿物为高Ti低Fe的TiFe合金, 内部出现由细粒状低Ti高Fe的TiFe合金和自然钛组成的蠕英结构.最外层由柯石英和蓝晶石组成的格架中分布细粒的Si金红石和Ti-Mg -K -Na -Ca氧化物.初步认为TiFe合金从深部高温高压环境往浅部上升过程中, 内部发生局部熔融, 分解出自然Ti, 并在其边部与其他硅酸岩矿物或熔体发生反应, 形成柯石英和蓝晶石.这一过程可能发生在洋脊拉张环境, 由于地幔柱的上涌, 将深部的豆荚状铬铁矿带到浅部, 使得其中包裹的一些高温高压环境下稳定的矿物变得不稳定, 发生熔融和交代反应, 形成新的不平衡的矿物组合.罗布莎柯石英的这种不寻常产出特征说明是在减压过程中形成, 不同于造山带中常见的由板块俯冲增压过程中形成的柯石英
- 柯石英 /
- 钛铁合金 /
- 豆荚状铬铁矿 /
- 罗布莎蛇绿岩 /
- 青藏高原
Abstract: Coesite and kyanite are new discovery from the podiform chromitite in the Luobusha ophiolite, which is located (about) 200 km southeast of Lhasa, Tibet, and marks the locus of collision between the Indian and Eurasian plates. Coesite-kyanite crystals are acicular and individuals are about (20-40) μm× (4-6) μm in size, forming a 30-50 μm wide rim (around) a 0.7 mm×0.5 mm TiFe alloy. Besides the coesite-kyanite rim, the TiFe alloy core is surrounded by a TiSi outer zone of about 10 μm width, and a native Ti inner zone of about 20-70 μm width. Ti-Mg-K-Na-Ca oxide crystals and Si-(rutile) occur as interstitial materials within the framework formed by coesite and kyanite. Within the TiFe alloy core are some small grains of native Ti and relatively low-Ti TiFe alloy, constituting a myrmekitic texture. The amount of Si, Al and O shows a decreasing trend from rim to core, which suggests that a chemical reaction occurred at the rim of the TiFe alloy. During this reaction new minerals formed with a symplektic texture. The regular variation from native Ti through TiSi to coesite-kyanite and oxide aggregates suggests that the series of minerals were formed by a reaction between native Ti and some silicates, under high pressure and temperature. This reaction probably occurred during the upwelling of a plume which carried TiFe alloy and other minerals from the deep mantle, suggesting that the Luobusha coesite formed during a decrease in pressure, which is in contrast with the coesite formed by increasing pressure in a convergent margin.
- coesite /
- TiFe alloy /
- podiform chromitite /
- Luobusha ophiolite /
- Tibet plateau

HTML全文

图 1 西藏罗布莎蛇绿岩的位置和地质图(据Malpas et al., 2003修改)

Fig. 1. Location and geological map of the Luobusha ophiolite, Tibet

下载: 全尺寸图片幻灯片

图 2 TiFe合金为主体的颗粒背散色图像(BSE-image)

TiFe合金颗粒从内至外被3个带所环绕，分别是: (1)自然钛; (2)TiSi合金; (3)柯石英-蓝晶石为主的硅酸岩和氧化物带.柯石英-蓝晶石为主的硅酸岩和氧化物带主要在图的左下最外层(暗色部分)(A); 自然钛带发育最完全，几乎围绕了整个颗粒(深灰色)(B); 钛硅合金(Ti_6.9Fe_0.2Si_2.8)为仅仅宽约10 μm的带，位于(1)和(3)带之间，从BSE图像中与自然钛不易区分，由图C中分析点14, 15, 16所控制，分析点12成分已是自然钛; 主体钛铁合金(Ti_6.2Si_0.3Fe_3.4)中出现由自然钛(暗色)和相对低Ti的钛铁合金(Ti_5.5Si_0.1Fe_3.9)组成的蠕英构造(D)

Fig. 2. BSE-image of a large TiFe alloy

下载: 全尺寸图片幻灯片

图 3 能谱(EDS) 柯石英-蓝晶石带的元素分布(位置与图 2c同)

外带显示Si、Al和O为主, Si高于Al, 反映柯石英的量远远高于蓝晶石, 带中靠近自然钛部分出现少许Ti, 远离则减少, K、Mg和Na只出现在柯石英-蓝晶石带; 自然钛带与柯石英-蓝晶石带之间有一薄层Si, 代表TiSi合金带; Fe仅仅在TiFe合金中出现

Fig. 3. EDS compositional maps of the coesite-kyanite belt

下载: 全尺寸图片幻灯片

图 4 柯石英和蓝晶石的代表性激光拉曼谱分析

c.柯石英的强峰和弱峰; k.蓝晶石的强峰和弱峰

Fig. 4. Representative Raman spectra of coesite and kyanite at the outer rim of TiFe alloy from the Luobusha podiform chromitite, Tibet

下载: 全尺寸图片幻灯片

图 5 TiFe合金在减压及与硅酸岩的化学反应过程中成分的变化

Fig. 5. Element migration diagram during chemical reaction between native Ti and silicate

下载: 全尺寸图片幻灯片

表 1 罗布莎豆荚状铬铁矿中TiFe合金及伴生矿物成分分析

Table 1. Composition of TiFe alloy and associated minerals in Luobusha podiform chromitite

参考文献(65)

[1]	Bai, W.J., Fang, Q.S., Zhang, Z.M., et al., 2001a. Crystal structure of forstertite from podiform chromitite in Luobusha ophiolite of Tibet and its implications. Acta Petrol. Mineral. , 20(1): 1-9(in Chinese with English abstract).
[2]	Bai, W.J., Yang, J.S., Fang, Q.S., et al., 2001b. Study on a storehouse of ultrahigh pressure mantle minerals—podiform chromite deposits. Earth Sci. Front. , 8(3): 111-121(in Chinese with English abstract).
[3]	Bai, W.J., Zhou, M.F., Fang, Q.S., 2000. Origin of podiform chromitites, diamonds and associated mineral assemblage in the Luobusha ophiolite, Tibet. Seismological Press, Beijing, 1-98(in Chinese).
[4]	Bai, W.J., Zhou, M.F., Robinson, P.T., et al., 1993. Possible diamond-bearing mantle peridotites and chromites in the Luobusha and Dongqiao ophiolites, Tibet. Canadian Journal of Earth Sciences, 30: 1650-1659. doi: 10.1139/e93-143
[5]	Belousova, E.A., Griffin, W.L., Pearson, N.J., 1988. Trace element composition and cathodoluminescence properties of southern African kimberlitic zircons. Mineral. Mag. , 62 (3): 355-366. https://www.researchgate.net/publication/233659847_Trace_element_composition_and_cathodoluminescence_properties_of_southern_African_kimberlitic_zircons
[6]	Cao, E.T.C., Shoemaker, E.M., Madsen, B.M., 1960. First natural occurrence of coesite. Science, 132: 220-221. doi: 10.1126/science.132.3421.220
[7]	Chopin, C., 1984. Coesite and pure pyrope in high-grade bluschists of the western Alps: A first record and some consequences. Contrib. Mineral. Petrol. , 86: 107-110. doi: 10.1007/BF00381838
[8]	Cong, B.L., 1995. Ultrahigh pressure metamorphic rocks in China. Episodes, 18: 91-94. doi: 10.18814/epiiugs/1995/v18i1.2/020
[9]	Drury, M.R., Gerald, J.D.F., 1998. Insights from laboratory studies of deformation and phase transition in the Earth's mantle. In: Ian J., ed., Mantle geology. Cambridge University, 503-559.
[10]	Fang, Q.S., Bai, W.J., 1981. Discovery of Alpine-type diamond-bearing ultrabasic inclusions in Tibet. Geol. Review, 45(5): 447-455(in Chinese with English abstract).
[11]	Goarant, F. Guyot, F., Peyronneau, J., et al., 1992, High-pressure and high temperature reaction between silicates and liquid iron alloys, in the diamond anvil cell, studied by analytical electron microscopy. J. Geophys. Res. , 97: 4477-4487. doi: 10.1029/92JB00018
[12]	Hazen, R.M., Finger, L.W., 1979. Crystal structure and compressibility of zircon at high pressure. Amer. Mineral. , 64: 196-201. https://pubs.geoscienceworld.org/msa/ammin/article-abstract/64/1-2/196/104641/Crystal-structure-and-compressibility-of-zircon-at
[13]	Kawada, K., 1977. The system Mg₂SiO₄-Fe₂SiO₄ at high pressure and temperature and Earth's interior. Ph. D. Thesis. Univ. of Tokyo, Tokyo, Japan.
[14]	Knittle, E., Jeanloz, R., 1989. Simulating the core-mantle boundary: An experimental study of high-pressure reaction between silicates and liquid iron. Geophys. Res. Lett. , 16: 609-612. doi: 10.1029/GL016i007p00609
[15]	Knittle, E., Jeanloz, R., 1991. Earth's core-mantle boundary: Results of experiments at high pressures and temperature. Science, 25: 1438-1443.
[16]	Liou, J.G., Wang, Q., Zhai, M., et al., 1995. Ultrahigh-pressure metamorphic rocks and their associated lithologies from the Dabie mountains, Central China: A field symposium. Chinese Science Bulletin, 40: 1-71. doi: 10.1360/csb1995-40-1-1
[17]	Liou, J.G., Zhang, R.Y., 1996. Occurrence of intergranular coesite in Sulu ultrahigh-pressure rocks from China: Implications for fluid activity during exhumation. Amer. Mineral. , 81: 1217-1221. doi: 10.2138/am-1996-9-1020
[18]	Liu, L.G., Bassett, W.A., Takahashi, T., 1974. Effect of pressure on the lattice parameter of stishovite. J. Geophys. Res. , 79: 1160-1164. doi: 10.1029/JB079i008p01160
[19]	Liu, L., 1975. Post-oxide phases of forstorite and enstatite. Geophys. Res. Lett. , (2): 417-419.
[20]	Liu, F.L., Xu, Z.Q., Liou, J.G., et al., 2002. Ultrahigh-pressure mineral inclusions in zircons from gneissic core samples of the Chinese Continental Scientific Drilling Site in eastern China. Eur. J. Mineral. , 14: 499-512. doi: 10.1127/0935-1221/2002/0014-0499
[21]	Malpas, J., Zhou, M.F., Robinson, P.T., et al., 2003. Geochemical and geochronological constraints on the origin and emplacement of the Yarlung-Zangbo ophiolites, southern Tibet. In: Dilek, Y., Robinson, P.T., eds., Ophiolites in Earth history. Geological Society of London Special Publications, 218: 191-206.
[22]	Meyer, H.O.A., Mccallum, M.E., 1986. Mineral inclusion in diamonds from the Sloanv kimberliters. Colorado J. Geol. , 94: 600-612.
[23]	Moore, G.O., Gurney, J.J., 1985. Pyroxene solid solution in garnets included in diamond. Nature, 335: 784-789. https://www.nature.com/articles/318553a0
[24]	O'Brien, P.J., Zotv, N., Law, R., et al., 2001. Coesite in Himalayan eclogite and implications for models of India-Asia collision. Geology, 29: 435-438.
[25]	Ogasawara, Y., Fukasawa, K., Maruyama, S., 2002. Coesite exsolution from supersilicic titanite in UHP marble from the Kokchetav massif, Northern Kazakhstan. Amer. Mineral. , 87(4): 454-461. doi: 10.2138/am-2002-0409
[26]	Schmidt, M., W., Stefano, P., Paola, C., et al., 1997. High-pressure behavior of kyanite: Decomposition of kyanite into stishovite and corundum. Amer. Mineral. , 82: 460-466. doi: 10.2138/am-1997-5-603
[27]	Smith, D.C., 1984. Coesite in clinopyroxene in the Caledonides and its implications for geodynamics. Nature, 310: 641-644. doi: 10.1038/310641a0
[28]	Smyth, J.R., Hazen, R.M., 1973. The crystal structure and hortonolite at several temperatures up to 900 ℃. Amer. Mineral. , 58: 588-593.
[29]	Sobolev, N.V., Snyder, G.A., Yefimova, E.S., et al., 1999. Composition and petrogenesis of Ti-oxides associated with diamond. Intern. Geol. Rev. , 41: 129-140. doi: 10.1080/00206819909465135
[30]	Sobolev, N.V., Fursenko, B.A., Goyainov, S.V., et al., 2000. Fossilized high pressure from the Earth's deep interior: The coesite-in-diamond barometer. Proc. Nat. Acad. Sci. , 97: 11875-11879. doi: 10.1073/pnas.220408697
[31]	Sobolev, N.V., Shatsky, V.S., 1990. Diamond inclusions in garnets from metamorphic rocks: A new environment for diamond formation. Nature, 343: 742-746. doi: 10.1038/343742a0
[32]	Sobolev, N.V., Shatsky, V.S., Valilov, M.A., 1992. Inclusions of diamond, coesite and co-existing minerals in zircons and garnet from metamorphic rocks of Kokchetav massif (northern Kazakhstan, USSR). Proc. 29th Int. Geol. Congr, 2599.
[33]	Stishov, S.M., Popova, S.V., 1961. New dense polymorphic modification of silica. Geochemistry, 10: 837-839.
[34]	Wan, X.Q. Luba, F.J., Massimo, S., 2002. Cretaceous and Paleogene boundary strata in southern Tibet and their implication for the India-Eurasia collision. Lethaia, 35: 131-145. doi: 10.1080/002411602320183999
[35]	Wang, H.S., Bai, W. J., Wang, B.X., et al., 1983. The chromite in China and its origin. Science Press, Beijing, 1 -248(in Chinese).
[36]	Wang, X.B., Bao, P.S., Deng, W.M., et al., 1987. Xizang (Tibet) ophiolites. Geological Publishing House, Beijing, 336(in Chinese).
[37]	Wang, X.M., Liou, J.G., Mao, H.G., 1989. Coesite-bearing eclogite from the Dabie Mountains in central China. Geology, 17: 1085-1088.
[38]	Xiao, X.C., 1984. The Xigaze ophiolite of southern Xizang(Tibet) and its relevant tectonic problems. In: Li, G.Q., Mercier, J.L., eds., The review about Himalaya between France and China. Geological Publishing House, Beijing, 143-163(in Chinese).
[39]	Xu, Z.Q., 1987. Etude tectonique et microtectonique de la chaine paleozoique et triasique des Qinlings(Chine). Academie de Montpellier Universite des Sciences et Techniques du Languedoc, 96-98.
[40]	Yagi, T., Akimoto, S., 1976. Direct determination of coesitestishovite transition by in situ X-ray measurements. Tectonophysics, 35: 259-270. doi: 10.1016/0040-1951(76)90042-1
[41]	Yang, F.Y., Kang, Z.Q., Liu, S.C., 1981. New octahedral pseudomorphs of lizardite and its origin. Acta Min. Sin. , 1: 52-54(in Chinese with English abstract).
[42]	Yang, J.S., Bai, W.J., Fang, Q.S., et al., 2002a. Silicon-rutile—An ultra-high pressure(UHP)mineral from an ophiolite. Progr. Natur. Sci. , 12(11): 1220-1222(in Chinese).
[43]	Yang, J.S., Song, S.G., Xu, Z.Q., et al., 2001. Discovery of coesite in the North Qaidam Early Paleozoic ultrahigh-high pressure metamorphic belt, NW China. Acta Geol. Sin. , 75(2): 175-179(in Chinese with English abstract). https://www.sciencedirect.com/science/article/pii/S1251805001017189
[44]	Yang, J.S., Xu, Z.Q., Wu, C.L., et al., 2002b. SHRIMP U-Pb dating on coesite-bearing zircon: Evidence for Indosinian ultrahigh-pressure metamorphism in Su-Lu, East China. Acta Geol. Sin. , 76(3): 354-372(in Chinese with English abstract). https://okayama.pure.elsevier.com/en/publications/shrimp-u-pb-dating-on-coesite-bearing-zircon-evidence-for-indosin
[45]	Yi, L.W., 1987. Geological significance of studying pseudomophous octahedral of serpentine and chlorite in ultramafic rocks. Acta Petrologica et Mineralogica, 6(4): 374-380 (in Chinese with English abstract).
[46]	Yu, S.C., Tung, S.F., Lee, J.S., et al., 2001. Structural and spectroscopic features of mantle-derived zircon crystals from Tibet. W. Paci. Earth Sci. , 1(1): 47-58.
[47]	Zhang, A.D., Xie, X.L., Guo, L.H., et al., 1991. Predicting minerals in diamond exploration and related data base. Science Press, Beijing, 1-122(in Chinese).
[48]	Zhang, H.Y., Ba, D.Z., Guo, T.Y., et al., 1996. The Luobusha chromite in Qusong, Tibet. Xizang Publishing House, Lhasa(in Chinese).
[49]	Zhang, J., Li, B., Utsumi, W., et al., 1996. In situ X-ray observations of the coesite-stishovite transition: Reversed phase boundary and kinetics. Phys. Chem. Miner. , 23: 1 -10. https://www.researchgate.net/publication/225893517_In_situ_X-ray_observations_of_the_coesite-stishovite_transition_Reversed_phase_boundary_and_kinetics
[50]	Zhou, M.F., Robinson, P.T., Malpas, J., et al., 1996. Podiform chromitites in the Luobusha ophiolite(Southern Tibet): Implications for melt-rock interaction and chromite segregation in the upper mantle. J. Petrol. , 37: 3-21. doi: 10.1093/petrology/37.1.3
[51]	Zhou, S., Mo, X.X., Mahoney, J.J., et al., 2002. Geochronology and Nd and Pb isotope characteristics of gabbro dikes in the Luobusha ophiolite, Tibet. Chinese Sci. Bull. , 47: 143 -146.
[52]	白文吉, 方青松, 张仲明, 等, 2001a. 西藏罗布萨蛇绿岩中豆荚状铬铁矿中镁橄榄石的晶体结构及其意义. 岩石矿物学杂志, 20(1): 1-9. https://www.cnki.com.cn/Article/CJFDTOTAL-YSKW200101000.htm
[53]	白文吉, 杨经绥, 方青松, 等, 2001b. 寻找超高压地幔矿物的储存库—豆荚状铬铁矿. 地学前缘, 8(3): 111-121. https://www.cnki.com.cn/Article/CJFDTOTAL-DXQY200103017.htm
[54]	白文吉, 周美付, 方青松, 等, 2000. 西藏罗布莎豆荚状铬铁矿、金刚石及伴生矿物成因. 北京: 地震出版社, 1-98.
[55]	方青松, 白文吉, 1981. 西藏首先发现金刚石的阿尔卑斯型岩体特征. 地质论评, 45(5): 447-455. doi: 10.3321/j.issn:0371-5736.1981.05.011
[56]	王恒升, 白文吉, 王炳熙, 等, 1983. 中国铬铁矿及其成因. 北京: 科学出版社, 1-248.
[57]	王希斌, 鲍佩声, 邓万明, 等, 1987. 西藏蛇绿岩. 北京: 地质出版社, 336. https://www.cnki.com.cn/Article/CJFDTOTAL-DZXE200711010.htm
[58]	肖序常, 1984. 藏南日喀则蛇绿岩以及有关的大地构造问题. 见: 李光芩, 麦尔西叶, J.L., 中法喜马拉雅考察成果. 北京: 地质出版社, 143-163.
[59]	杨凤英, 康志勤, 刘淑春, 1981. 蛇纹石中八面体假象及其成因初步讨论. 矿物学报, 1: 52-54. doi: 10.3321/j.issn:1000-4734.1981.01.009
[60]	杨经绥, 白文吉, 方青松, 等, 2002a. 蛇绿岩中的一种超高压矿物—硅金红石. 自然科学进展, 12(11): 1220-1222. https://www.cnki.com.cn/Article/CJFDTOTAL-ZKJZ200211028.htm
[61]	杨经绥, 宋述光, 许志琴, 等, 2001. 柴达木盆地北缘早古生代高压-超高压变质带中发现典型超高压矿物—柯石英. 地质学报, 75(2): 175-179. https://www.cnki.com.cn/Article/CJFDTOTAL-DZXE200102004.htm
[62]	杨经绥, 许志琴, 吴才来, 等, 2002b. 含柯石英锆石的SHRIMP U-Pb定年: 胶东印支期超高压变质作用的证据. 地质学报, 76(3): 354-372. https://www.cnki.com.cn/Article/CJFDTOTAL-DZXE200203010.htm
[63]	易隶文, 1987. 研究超镁铁岩中八面体假象蛇纹石和绿泥石的地质意义. 岩石矿物学杂志, 6(4): 374-380. https://www.cnki.com.cn/Article/CJFDTOTAL-YSKW198704014.htm
[64]	张安棣, 谢锡林, 郭立鹤, 等, 1991. 金刚石找矿指示矿物研究及数据库. 北京: 科学出版社, 1-122.
[65]	张浩勇, 巴登珠, 郭铁鹰, 等, 1996. 西藏自治区曲松县罗布萨铬铁矿研究. 拉萨: 西藏人民出版社.