Microsoft Word - 8-武海-L.doc

Size: px

Start display at page:

Download "Microsoft Word - 8-武海-L.doc"

亚焦
5 years ago
Views:

1 doi: /j.ddgzyckx (Volume)40, (Number)5, (SUM)154 (Pages)975~985, 2016, 10(October, 2016) 大地构造与成矿学 Geotectonica et Metallogenia 1, 武海 2 1,, 董亚林 3, 许瑞梅 3, 赵文霞 (1., ; 2., ; 3., ) 3* 摘要 :,,, /, /, Ti 4+ (Fe 2+ Si 4+ )=2Ca 2+, / 关键词 : ; HP/UHP ; ; 中图分类号 : P581 文献标志码 : A 文章编号 : (2016) 引言, (, 2006a, 2008), /, / ( ) /, , >200 km (, 2003) Song et al. (2004), >200 km, Liu et al. (2007),, 12~14 GPa, / >200 km >350 km (2013) EBSD,,, 427~ GPa(, 2006b 2008;, 2009),, ( 1),, 收稿日期 : ; 改回日期 : 项目资助 : ( ) 第一作者简介 : (1989 ),,, @qq.com 通信作者 : (1962 ),,, zhaowx@mail.sysu.edu.cn

2 976 第 40 卷 Fig.1 1 (, 2013 ) Plate tectonic sketch map of the Qiangtang HP metamorphic belt in North Tibet, 1 地质概况,,,,,, ;,, ( ), (, 2009), 500 km,,, 榴辉岩中矿物出溶体及实验条件,,,,, JEOL JXA8800R, FEI Quanta400F, Oxford Inca, Maping : 15 kv, A, Focus ( 60 nm); : 20 kv, 6, Spot Size 5 μm 3 石榴子石中矿物出溶体特征及出溶机制 3.1, 1~2 μm, 1 μm, 10 μm ( 2a, b),,, 120,

3 第 5 期武海等 : 羌塘地区榴辉岩中矿物出溶体及其成因机制探讨 977, 2~5 μm( 2e, f), 10 μm,, ( 2e, f), ( 5), Ti ( 3, 4),, TiO 2 ( 1), ( 2a, b) (a) (b) ; (c) (d) ( ); (e) (f) ( ) : Grt. ; Rt. ; Ap. ; Q. ; Hb. Fig.2 2 Planepolarized light/bse images of minerals with exsolution lamellae in the eclogite

of rutile in the garnet 石榴子石中针状金红石和石英特征及其出溶红石的针状或棒状体是由与金红石共生的石榴子石机制探讨裂解后又愈合所包裹而形成 Hwang et al.

4 第 40 卷 978 Fig.3 Fig 图 3 石榴子石中金红石出溶体能谱图 EDS spectra of the exsolution rods of rutile in the garnet 图 4 石榴子石中金红石出溶体电子探针面扫描分析图 EPMA mapping analysis of the exsolution rods of rutile in the garnet 石榴子石中针状金红石和石英特征及其出溶红石的针状或棒状体是由与金红石共生的石榴子石机制探讨裂解后又愈合所包裹而形成 Hwang et al. (2007)对苏鲁超高压带仰口超高压实验研究表明(Ringwood and Major, 1971; 榴辉岩的石榴子石中金红石针状(棒状)出溶体进行 Tompsom, 1975), 石榴子石在超高压条件下可以溶入了电子显微(AEM)研究, 提出金红石出溶的三种机大量 Ti, Na 和 P 等元素, 从而形成富含这些元素的石榴制 : (1)出溶金红石由先前存在的先导矿物继承而子石, 其置换方式为: PIV+NaVIII SiIV+CaVIII; NaVIII+ 来; (2)出溶金红石通过分解再沉淀机制形成; (3)金 TiVI=CaVIII+Al VI, 形成分子式如(CaNa 2 )Ti 2 Si 3 O 12 和

5 第 5 期武海等 : 羌塘地区榴辉岩中矿物出溶体及其成因机制探讨 979 Fig.5 5 EPMA mapping analysis of the exsolution rods of quartz and amphibole in the garnet 表 1 石榴子石中金红石出溶体电子探针分析结果 (%) Table 1 Microprobe analysis of chemical compositions (%) of the exsolution rods of rutile in the garnet No. Na 2 O Cr 2 O 3 K 2 O MgO MnO CaO Al 2 O 3 FeO TiO 2 SiO 2 NiO Total (Ca 2 Na)(Al, Ti)Si 3 O 12 (Tompsom, 1975;, 2007) 5~15 GPa, (Ringwood and Major, 1971), (2003),,, : M 30.5n0.5x (Al 2nx Si n Ti x )(Si 3y Ti y )O 12 ( )=[(1 n)/2 x/2]m 3 Al 2 Si 3 O 12 ( )+(n/2+x/2)m 2 Si 2 O 6 ( )+(x+y)tio 2 ( )+ [3n/2+x/(2 y)]sio 2 ( ) n+x (Si, Ti) V +0.5 (II) = Al V +0.5M (II) M 2.5 [Al(Si, Ti)]Si 3 O 12 [3n/2+x/(2 y)] 0,, 3(n+x)/2, Ti,, (65.21%~71.68%), (3.69%~11.58%), (2.35%~9.03%),

6 980 第 40 卷表 2 羌塘榴辉岩中高钛石榴子石和正常石榴子石电子探针分析结果 (%) Table 2 Microprobe analysis of chemical compositions (%) of high Ti garnet and common garnet in the eclogite ( Ti) ( ) SiO TiO FeO Al 2 O CaO MnO MgO K 2 O Cr 2 O Na 2 O NiO Total O=24 Si Ti Fe Al Ca Mn Mg K Cr Na Ni (15.64%~22.56%), (0.69%~3.05%), Ti, / Ti, ( 6) / / Ti Ti Ti, TiO %~0.31%, TiO 2 0.1%, 0.2%,, / TiO %~ 0.09%, 0.1% Ti, Ti, Al, Ca ( 2) Zhang et al. (2003) Ti,, Ti, Ca, Mg, Si Al, : Ca 2+ Ti 4+ 2Al 3+ Si 4+ Mg 2+ 2Al 3+, Ti ( TiO 2, 0.8%~4.5%) Grt Ti /Cpx Ti 5~15 GPa,, /,,,, Ti,, 2,, Si Ti Ca

第 5 期武海等 : 羌塘地区榴辉岩中矿物出溶体及其成因机制探讨 981 6 TiO 2 Fig.6 Changes of TiO 2 contents in garnet with exsolution rods of rutile, Ca 2+ Ti 4+ 2Al 3+ Si 4+ Mg 2+ 2Al 3+ Al Si, Ti, : M 30.5n0.

7 第 5 期武海等 : 羌塘地区榴辉岩中矿物出溶体及其成因机制探讨 TiO 2 Fig.6 Changes of TiO 2 contents in garnet with exsolution rods of rutile, Ca 2+ Ti 4+ 2Al 3+ Si 4+ Mg 2+ 2Al 3+ Al Si, Ti, : M 30.5n0.5x (Al 2nx Si n Ti x )(Si 3y Tiy)O 12 ( )= [(1 n)/2 x/2]m 3 Al 2 Si 3 O 12 ( )+(x+y)tio 2 ( )+(n/2+x/2)m 2 Si 2 O 6 ( )+[3n/2+x/(2 y)] SiO 2 ( )(, 2003),, ( 2f), 4 磷灰石中金红石成分出溶体特征及其出溶机制 4.1, 1~5 μm ( 7),, ( 8) ( 2c),,, ( 3) 4.2,,,,, 1999 (Zhang and Liou, 1999) CuS 2 ( Massonne, 2005; Fig.7 7 The EDS spectra of the exsolution rods of rutile in apatite

8 982 第 40 卷 Fig.8 8 EPMA mapping analysis of the exsolution rods of rutile in apatite 表 3 磷灰石及其金红石出溶体电子探针分析结果 (%) Table 3 Microprobe analysis of chemical compositions (%) of apatite and the exsolution rods of rutile in apatite P 2 O SiO TiO Al 2 O CaO NiO MgO Cl FeO Na 2 O K 2 O MnO F Total O=24 P Si Ti Al

第5期武海等: 羌塘地区榴辉岩中矿物出溶体及其成因机制探讨 983 续表 3: 磷灰石分析点磷灰石中金红石出溶体 1 2 3 4 5 1 2 Ca 8.712 8.790 8.829 Ni 0.006 Mg 0.000 0.002 Cl 0.003 3 4 5 8.814 8.717 3.693 0.002 3.445 3.052 3.146 3.350 0.007 0.002 0.

9 第5期武海等: 羌塘地区榴辉岩中矿物出溶体及其成因机制探讨 983 续表 3: 磷灰石分析点磷灰石中金红石出溶体 Ca Ni Mg Cl Fe Na K Mn F 梁凤华等, 2006; 陈晶等, 2006; 汤倩等, 2006a, 在磷灰石颗粒核部位置(图 9c) 阴极发光显示磷灰 2006b) 而磷灰石中出溶金红石还未见报道, 本文研石具有成分环带特征(图 9a b), 荧光图像显示磷灰究磷灰石为氟磷灰石, F 含量较高, 达到 3.1%~4.0%, 石核部呈黄绿色荧光, 阴极发光图像(CL)也很好地 TM 证实了这一特征, 并且我们发现, 含有金红石出溶 Field Emission Scanning Electron Microscope)中的阴体的核部(即呈黄绿色荧光)在 CL 图像中均显示较暗极发光系统(Cathodoluminescence)观察出溶体出现亮度(图 9c d) 磷灰石的这种环带结构证实了其变而 Cl 的含量极低运用扫描电镜(ZEISSΣIGMA (a), (b)不含出溶体磷灰石阴极发光图像; (c), (d)含有出溶体磷灰石阴极发光图像 Fig.9 图 9 磷灰石阴极发光(CL)图像 Cathodoluminescence (CL) images of apatite

10 984 第 40 卷, Fe Si, FeO 0.25%, 0.11% Ti, (, 2003), Ti Fe Si,, Fe Si, 髙, Ti (White et al., 2005), A 10 (ZO 4 )6X 2, A Ca 2+ Sr 2+ Mn 2+ Fe 2+ Mg 2+ Ba 2+ Eu 2+ REE 3+ Al 3+ Na + Ce 4+, Z P 5+ Si 4+ S 6+ V 5+ Al 3+, X F Cl OH, A Z X Ca : Ca1 Ca2, (, 2003), Ti, / Ti(Fe Si) Ti 4+ (Fe 2+ Si 4+ )=2Ca 2+, ( 9), /,, Ti, Fei (1998), Fei (1998), 5 结论, Si Mg Ti,, /, / Ti Ca, /, 致谢 : 中国地质科学院地质研究所张泽明研究员和中国地质大学 ( 武汉 ) 章军锋教授审阅了全文并提出宝贵意见, 在此表示感谢参考文献 (References):,,, , 22(7): , , 19( ): ,, William C T, , 23(3): ,,. 2006b. // 2006.,,,, , 27(1): ,,,. 2006a.., 51(1): ,,, , 22(2): ,,, , 52(18): ,,, ( ). : : ,,,,,,. 2006a. (CCSD)., 22(7): ,,,,,,.

11 第 5 期武海等 : 羌塘地区榴辉岩中矿物出溶体及其成因机制探讨 b. (CCSD) UThPb., 22(7): , ( ), 25(4): ,, , 28(12): , Massonne H J , 21(2): Fei Y W Solid solutions and element partitioning at high pressures and temperatures. Review in Mineralogy, 37: Hwang S L, Yui T F and Chu H T On the origin of oriented rutile needles in garnet from UHP eclogites. Journal of Metamorphic Geology, 25: Liu L, Zhang J F, Green II H W, Jin Z M and Bozhilov K N Evidence of former stishovite in metamorphosed sediments, implying subduction to >350 km. Earth and Planetary Science Letters, 263: Ringwood A E and Major A Synthesis of majorite and other high pressure garnets and perovskites. Earth and Planetary Science Letters, 12: Song S G, Zhang L F and Niu Y L Ultradeep origin of garnet peridotite from the North Qaidam ultrahigh Pressure belt, Northern Tibetan Plateau, NW China. American Mineralogist, 89: Tompsom R N Is uppermantle phosphorus contained in sodic garnet? Earth and Planetary Science Letters, 26: White T, Ferraris C, Kim J and Madhavi S Apatite An adaptive framework structure. Reviews in Mineralogy and Geochemistry, 57: Zhang R Y and Liou J G Exsolution lamellae in minerals from ultrahighpressure rocks. International Geology Review, 41: Zhang R Y, Zhai S M, Fei Y W and Liou J G Titanium solubility in coexisting garnet and clinopyroxene at very high pressure: The significance of exsolved rutile in garnet. Earth and Planetary Science Letters, 216: Mineral Exsolution and its Genetic Significance of the SongduoQiangtang Eclogite in QinghaiTibet WU Hai 1, 2, DONG Yalin 1, 3, XU Ruimei 3 and ZHAO Wenxia 3* (1. School of Earth Science and Geological Engineering, Sun Yatsen University, Guangzhou , Guangdong, China; 2. Hongshi Holding Group Co., Ltd, Jinhua , Zhejiang, China; 3. Instrumental Analysis and Research Center, Sun Yatsen University, Guangzhou , Guangdong, China) Abstract: Recent studies have shown that garnet and apatite with needlelike exsolution lamellae are widely found in the eclogites from the central Qiangtang metamorphic belt. Needlelike exsolution lamellae of rutile, quartz and amphibole are identified in garnet and apatite by electron microprobe (EPMA), scanning electron microscope (SEM) and Xray energydispersive (EDS) analyses. The garnet may have experienced HP/UHP metamorphism. We find for the first time apatite with exsolution of rutile that may have been formed by the replacement of Ti 4+ (Fe 2+, Si 4+ )=2Ca 2+ under high pressure or ultrahigh pressure conditions. These exsolution lamellae in garnet and apatite imply that the Qiangtang eclogite may have experienced HP/UHP metamorphism. Keywords: Qiangtang, Tibet; HP/UHP eclogite; exsolution lamellae; UHP metamorphism

AL O 2SiO 2H O AL O 2SiO + 2H O CaCO3 + CaO CO2 CaSO4 + CaO SO3 CaSO3 + CaO SO2 2AL O + 6SiO 3AL O 2SiO + 4SiO

AL Si O OH 4 2 2 5 K AL Si O 2 3 8 2 3 8 2 3 8 Na AL Si O Ca AL Si O AL O 2SiO 2H O AL O 2SiO + 2H O 2 3 2 2 2 3 2 2 CaCO3 + CaO CO2 CaSO4 + CaO SO3 CaSO3 + CaO SO2 2AL O + 6SiO 3AL O 2SiO + 4SiO 2 3 2