Journal of Tropical Oceanography >
Petrography of carbonate veins in basement basalts from the South China Sea Exp. 349
Received date: 2018-01-09
Online published: 2018-12-24
Supported by
National Natural Science Foundation of China (91428102, 41876064);IODP China funding for Exp. 349 and 367
Copyright
The basaltic basement in the South China Sea was cored for the first time during International Ocean Discovery Program (IODP) Exp 349. The basalt was collected from Sites U1431 and U1433 close to the fossil spreading ridge in East and Southwest Sub-basins, respectively. Carbonate veins (n=16) within the basalt were investigated under microscope and by the laser Raman spectra. At Site U1431, the carbonate veins consisted of calcite veins or aragonite veins, while at Site U1433 the carbonate veins are composed of either calcite veins, or aragonite veins, and calcite-aragonite mixed veins. Meanwhile, the calcite veins and aragonites alternated, and at ~42.1 m below basement, two calcite veins and one aragonite vein occurred parallel, likely indicating that multiple hydrothermal fluids of different sources have circulated there. At both sites, the textures of aragonite are generally the same-blocky, fibrous, and radiating fibers. However, it is not the case for calcite. At Site U1431, the calcite is clotted blocky, blocky, granule, and fibrous, while at Site U1433 the calcite only occur as blocks. The abundance of carbonate veins at Site U1431 is much higher than that at Site U1433. These suggest that the low-temperature hydrothermal circulation at Site U1431 is stronger than that at Site U1433. Different local geology and environment mostly lead to the differences in hydrothermal activity at these two sites: Site U1431 is close to a giant seamount that serves as a recharge site, while Site U1433 is far away from any recharge or discharge site.
XU Jiarui , CHEN Yifeng , WANG Baoyun . Petrography of carbonate veins in basement basalts from the South China Sea Exp. 349[J]. Journal of Tropical Oceanography, 2018 , 37(6) : 63 -73 . DOI: 10.11978/2018007
Fig. 1 Map of Sites U1431 and U1433 in the South China Sea (IODP Exp. 349). Modified from Li et al (2015a)图1 南海IODP 349航次U1431和U1433站位图(改编自Li et al, 2015a) |
Fig. 2 Typical carbonate veins within basalt from Sites U1431 and U1433 in the South China Sea图2 南海U1431和U1433站位典型的基底碳酸盐岩脉 |
Fig. 3 Abundance of carbonate veins vs. depth: |
Fig. 4 Other minerals besides carbonate minerals in carbonate veins. |
Fig. 5 Different shapes and the Raman spectra of carbonate minerals in carbonate veins at Site U1431图5 U1431站位碳酸盐岩脉的不同集合体形状的碳酸盐矿物及对应的拉曼光谱 |
Tab. 1 Raman shifts of carbonate minerals from the South China Sea表1 南海碳酸盐岩脉的碳酸盐矿物拉曼位移 |
岩脉编号 | 深度/mbsf | 基底深度/m | 碳酸盐矿物结构 | 矿物相 | 晶格振动 | 内部振动 | ||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|
平动 | 摆动 | 面内弯曲振动 | 对称伸缩振动 | 反对称伸缩振动* | 面外弯曲振动* | |||||||
U1431E- | 39R-1-W, 10-13 | 910.12 | 20.41 | 块状 | 文石 | 153 | 206 | 706 | 1086 | 1463 | / | |
41R-2-W, 43-47 | 925.38 | 35.67 | 斑块状 | 方解石 | 155 | 283 | 713 | 1088 | / | / | ||
粒状 | 方解石 | 154 | 282 | 713 | 1089 | / | / | |||||
41R-5-W, 21-23 | 928.67 | 38.96 | 纤维状/放射纤维状 | 文石 | 153 | 206 | 703 | 1085 | 1463 | / | ||
41R-5-W, 21-23 | 928.67 | 38.96 | 粒状 | 文石 | 153 | 206 | 704 | 1086 | / | / | ||
41R-7-W, 65-71 | 931.84 | 42.13 | 纤维状 | 方解石 | 155 | 282 | 713 | 1087 | / | 1749 | ||
纤维状/放射纤维状 | 文石 | 154 | 206 | 706 | 1085 | 1463 | / | |||||
块状 | 文石 | 153 | 207 | 706 | 1086 | / | / | |||||
42R-4-W, 31-35 | 937.66 | 47.95 | 块状 | 方解石 | 156 | 284 | 713 | 1088 | / | 1749 | ||
斑块状 | 方解石 | 153 | 282 | 712 | 1087 | / | 1749 | |||||
43R-2-W, 74-77 | 944.66 | 54.94 | 块状 | 方解石 | 155 | 283 | 713 | 1087 | / | / | ||
46R-3-W, 114-118 | 976.16 | 86.45 | 块状 | 方解石 | 154 | 283 | 713 | 1087 | 1438 | / | ||
47R-5-W, 5-9 | 987.22 | 97.51 | 块状/放射纤维状 | 文石 | 152 | 205 | 705 | 1084 | 1463 | / | ||
49R-2-W, 136-138 | 993.88 | 104.17 | 纤维状 | 方解石 | 155 | 282 | 713 | 1087 | 1438 | 1749 | ||
粒状 | 方解石 | 156 | 283 | 712 | 1088 | / | / | |||||
50R-3-W, 6-10 | 1003.80 | 114.09 | 纤维状 | 方解石 | 155 | 282 | 713 | 1087 | 1438 | 1749 | ||
U1433B- | 66R-1-W, 63-65 | 805.84 | 10.34 | 块状 | 方解石 | 155 | 282 | 713 | 1087 | / | 1749 | |
纤维状 | 文石 | 152 | 206 | 705 | 1084 | / | / | |||||
块状 | 文石 | 153 | 206 | 705 | 1084 | / | / | |||||
66R-4-W, 11-16 | 809.38 | 13.88 | 块状 | 文石 | 152 | 206 | 704 | 1084 | 1461 | / | ||
66R-4-W, 109-114 | 810.36 | 14.86 | 块状 | 方解石 | 155 | 281 | 712 | 1087 | 1437 | 1749 | ||
块状 | 文石 | 152 | 206 | 704 | 1084 | 1461 | / | |||||
纤维状/放射纤维状 | 文石 | 152 | 205 | 704 | 1084 | / | / | |||||
68R-1-W, 86-90 | 820.58 | 25.08 | 块状 | 方解石 | 155 | 283 | 713 | 1087 | / | / | ||
放射纤维状/块状 | 文石 | 152 | 206 | 705 | 1084 | / | / | |||||
75R-1-W, 120-122 | 854.91 | 59.41 | 块状 | 方解石 | 155 | 282 | 713 | 1087 | / | / | ||
75R-3-W, 31-34 | 856.13 | 60.63 | 块状 | 方解石 | 155 | 282 | 713 | 1087 | 1437 | 1749 |
注: *谱峰强度非常弱, 不易被检测到; “/”表示未检测到。 |
Fig. 6 Textures and the Raman spectra of calcite-aragonite co-precipitating veins at Site U143图6 U1433站位方解石-文石共生脉及对应的拉曼光谱 |
Fig. 7 Typical structures of carbonate veins. |
Fig. 8 Schematic illustration of the ridge-flank hydrothermal flow and circulation at Site U1431 close to the fossil ridge of the South China Sea. |
The authors have declared that no competing interests exist.
[1] |
|
[2] |
|
[3] |
|
[4] |
|
[5] |
|
[6] |
|
[7] |
|
[8] |
|
[9] |
|
[10] |
|
[11] |
|
[12] |
|
[13] |
|
[14] |
|
[15] |
|
[16] |
|
[17] |
|
[18] |
|
[19] |
|
[20] |
|
[21] |
|
[22] |
|
[23] |
|
[24] |
|
[25] |
|
[26] |
|
[27] |
|
[28] |
|
[29] |
|
[30] |
|
[31] |
|
[32] |
|
[33] |
|
[34] |
|
[35] |
|
[36] |
|
/
〈 |
|
〉 |