中国大陆科学钻探主孔高铁钛榴辉岩的磁性岩石学

曾庆理; 刘庆生; 邱宁

中国大陆科学钻探主孔高铁钛榴辉岩的磁性岩石学

中国地质大学地球物理与空间信息学院，湖北武汉 430074

基金项目:

国家自然科学基金项目 40474025

国家自然科学基金项目 90714002

详细信息

作者简介:
曾庆理（1984—）男博士从事岩石磁学研究

通讯作者:
刘庆生, E-mail: lqs321@cug.edu.cn

中图分类号: P584
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出版历程
- 收稿日期: 2009-06-23
- 刊出日期: 2009-11-25

Magnetic Petrology of the High Fe-Ti Eclogite from the Chinese Continental Scientific Drilling(CCSD) Main Hole

Institute of Geophysics and Geomatics, China University of Geosciences, Wuhan 430074, China

摘要

摘要: 中国大陆科学钻探(CCSD) 主孔中318~380m (A)、420~470m (B) 和530~600m (C) 深度分布三段高铁钛榴辉岩, 它们具有高全铁(FeO_T) (平均15.36%、14.09%和20.83%)、高TiO₂ (平均3.89%、3.28%和4.10%) 和低SiO₂ (平均44.64%、48.64%和41.10%) 含量分布特征.岩石磁性测量结果表明, A段样品为低磁化率(平均3.61×10^-7m³·kg^-1)、低天然剩余磁化强度(平均0.12×10^-3Am²·kg^-1) 和低Q值(平均8.03);B段样品为高磁化率(平均12.55×10^-7m³·kg^-1) 和中等天然剩余磁化强度(平均1.47×10^-3Am²·kg^-1) 及Q值(平均26.42);C段样品磁化率介于A、B段之间(平均9.73×10^-7m³·kg^-1), 而天然剩余磁化强度(平均10.05×10^-3Am²·kg^-1) 和Q值(平均138.571) 最大.岩石磁学和岩相学研究表明, A、B两段样品代表了新鲜或轻度退变质榴辉岩的磁性特征, 但就研究的代表性样品的磁性岩石学特征而言, B段样品显示的退变质程度稍高于A段; C段榴辉岩样品密度最大, 主要为新鲜榴辉岩, 氧逸度明显高于A、B两段样品, 且存在大量出溶过程形成的以薄层结构为标志特征的赤铁矿-钛铁矿固溶体, 可能是样品高天然剩磁的主要原因.
- 高铁钛榴辉岩 /
- CCSD主孔 /
- 岩石磁学 /
- 赤铁矿-钛铁矿固溶体 /
- 磁化率
Abstract: The high Fe-Ti eclogites appear at the depth intervals from 318-380m (A), 420-470m (B) and 530-600m (C) respectivelys in the Chinese Continental Scientific Drilling (CCSD) Project main hole. They have high FeO_T (total Fe) abundances of average 15.36%, 14.09% and 20.83%, high TiO₂ concentration of average 3.89%, 3.28% and 4.10% and low SiO₂ contents of average 44.64%, 48.64% and 41.10%, respectively. Magnetic study of the samples shows that section A has the lowest susceptibility (average 3.61×10^-7m³·kg^-1), NRM (average 0.12×10^-3Am²·kg^-1) and Q-value (average 8.03); section B has the highest susceptibility (average 12.55×10^-7m³·kg^-1), medium NRM (average 1.47×10^-3Am²·kg^-1) and Q-value (average 26.42); section C samples has medium susceptibility (average 9.73×10^-7m³·kg^-1) and the highest NRM (average 10.05×10^-3Am²·kg^-1) and Q-value (average 138.571). The magnetic property compared with metamorphic petrology of high Fe-Ti eclogites suggests that section A samples represent magnetic properties of the fresh or slightly retrograded eclogites; section B samples show higher metamorphic retrogression than those of section A; section C samples are fresh eclogite, whose density and oxygen fugacity are distinctly higher than those of A and B, containing a lot of hematite-ilmenite lamellar textures formed during the slowly exhumation, which can be the main contributors to the high NRM of the section C eclogite.
- high Fe-Ti eclogite /
- CCSD main hole /
- rock magnetic /
- hematite-ilmenite solid solution /
- susceptibility

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图 1 三段榴辉岩典型样品的光学显微照片(反射光)

a.45号样(342.30 m); b.62号样(463.97 m); c.90号样(587.00 m).矿物代号: Grt.石榴石; Hem.赤铁矿; Ilm.钛铁矿; Omp.绿辉石; Pyr.黄铁矿; Rt.金红石; Sym.后成合晶; Timt.钛磁铁矿; Amp.角闪石

Fig. 1. Photomicrographs of representative samples from 3 subunits respectively

下载: 全尺寸图片幻灯片

图 2 磁性参量之间相互关系散点图

●代表A段榴辉岩; □代表B段榴辉岩; +代表C段榴辉岩

Fig. 2. Scattergrams of magnetic parameters for eclogite samples

下载: 全尺寸图片幻灯片

表 1 岩石的密度和磁性参数

Table 1. Density and magnetic parameters of samples

表 2 代表性样品的矿物组成(%)

Table 2. Mineral assemblage of representative samples

表 3 代表性样品的全岩化学成分主量元素成分分析结果

Table 3. Whole rock major element compositions of representative samples

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