Attitude Characteristics of Structure and Geological Meaning in 3 000m Core of the CCSD Main Hole
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摘要: 对CCSD主孔3 000 m岩心叶理、具断层擦痕的微断层及断层擦痕产状特征进行了统计分析, 并分析了脆、韧性剪切带的运动学特征, 研究表明(1) 榴辉岩类叶理产状明显较片麻岩类陡, 可能与其岩石能干性较强有关, 因而在挤压褶皱变形过程中表现出不同的变形行为.韧性变形主体表现为顺层剪切, 含断层擦痕的微断层最主要的一组产状与叶理面一致或接近一致, 部分伴随与之呈共轭关系的另一组微断层. (2) 脆、韧性变形以SEE-NWW向剪切为主, 部分为近SN向, 脆性、韧性变形域断层运动方向基本一致.但现在所保留下来的构造变形中韧性变形以SEE向NWW的逆冲型剪切为主, 部分为近SN向韧性剪切作用; 而脆性变形以NWW向SEE的正滑作用为主. (3) 主孔构造应力场初步可划分为4期, 现在所保留的主期构造为SEE-NWW向挤压构造应力场所致.Abstract: This article analyzes attitude characteristics of foliation, miniature faults with striation and striation of miniature faults, and kinematic characters of brittle and ductile shear zone. The results indicate that: (1) The dip angles of eclogite-type foliations are obviously steeper than the angles of gneiss-type foliations, because the strength of the former is higher than the latter, so deformation of both is different in compressional process; the main part of ductile deformation is shearing along foliation; attitude of the main part of miniature faults with striation is identical with foliation, part of it is accompanied by other miniature faults which are conjugate with the former. (2) The main part of brittle and ductile deformation shears in an ESE-WNW direction, with a small part shearing in a near S-N direction. The movement direction of faults in brittle and ductile deformation is the same, but in structures conserved now, the main part of the ductile deformation is dominated by the ESE-WNW thrust shear sense, part of it is ductile shearing of SN direction; the main part of brittle deformations is dominated by the WNW-ESE normal shear sense. (3) The tectonic stress field of main hole is divided initially into four periods, the main structure reserved now was coming from compressional tectonic stress field in an ESE-WNW direction.
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图 1 CCSD主孔3 000 m岩心叶理及微断层产状极点投影等值线图(吴氏网下半球投影)
Fig. 1. Projection diagram of the foliation pole and miniature faults in 3 000 m core of the CCSD main hole
图 2 CCSD主孔100~3 100 m岩心构造柱状图(许志琴等, 2004有变化)
1.榴辉岩类; 2.角闪岩类; 3.副片麻岩; 4.花岗质片麻岩; 5.超基性岩; 6.韧性或脆韧性剪切带及主要剪切指向; 7.脆性正断层
Fig. 2. Columnar section of structure in 100-3 100 m core of the CCSD main hole
图 3 CCSD主孔韧性剪切带剪切指向标志
a.B1534R6P40a, 3 016.5 m, 旋转碎斑体系示逆冲型剪切指向; b.B558R401P3aA, 1 012 m, 反Z型褶皱示逆冲型剪切指向; c.B359R286P1f, 695 m, 反Z型褶皱示逆冲型剪切指向; d.B789R548P3c, 1 312 m, 长英质脉不对称布丁构造示逆冲型剪切指向; e.B1153R60P28b, 2 262 m, 长英质脉不对称布丁构造示逆冲型剪切指向
Fig. 3. Shear sense markers of ductile shear zones from the CCSD main hole
图 4 CCSD主孔3 000 m岩心微断层擦痕产状投影等值线图(吴氏网下半球投影)
a.100~738 m逆断层擦痕投影图, N=52, 2%~4%~8%;b.738~1 012 m逆断层擦痕投影图, N=52, 2%~4%~8%;c.3 000 m逆断层擦痕投影图, N=697, 1%~2%~4%;d.3 000 m正断层擦痕投影图, N=1 259, 1%~2%~4%
Fig. 4. Projection diagram of striation attitude of miniature faults in 100-2 950 m core of the CCSD main hole
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