南沙海槽前陆盆地热流变结构

马辉; 许鹤华; 施小斌; 陈爱华; 刘唐伟

doi:10.3799/dqkx.2011.099

南沙海槽前陆盆地热流变结构

doi: 10.3799/dqkx.2011.099

马辉^{1, 2},
许鹤华^1, ,,
施小斌¹,
陈爱华^{1, 2},
刘唐伟^{1, 2}

1.
中国科学院南海海洋研究所边缘海地质重点实验室, 广东广州 510301
2.
中国科学院研究生院, 北京 100049

基金项目:

中国科学院知识创新工程重要方向项目群项目 KZCX2-YW-Q05-04

国家重点基础研究发展计划“973”项目 2007CB41170405

国家高技术研究发展计划“863”课题 2008AA09Z306

详细信息

作者简介:
马辉(1987—), 男, 硕士研究生, 从事盆地构造分析及地球动力学演化数值模拟研究

通讯作者:
许鹤华, E-mail: xhhcn@scsio.ac.cn

中图分类号: P738.6
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出版历程
- 收稿日期: 2011-05-28
- 刊出日期: 2011-09-15

Lithospheric Thermal-Rheological Structure of Nansha Trough Foreland Basin in South China Sea

MA Hui^{1, 2},
XU He-hua^{1
, ,},
SHI Xiao-bin¹,
CHEN Ai-hua^{1, 2},
LIU Tang-wei^{1, 2}

1.
CAS Key Laboratory of Marginal Sea Geology, South China Sea Institute of Oceanology, Guangzhou 510301, China
2.
Graduate University of Chinese Academy of Sciences, Beijing 100049, China

摘要

摘要: 为了研究南沙海槽前陆盆地深部岩石圈的热力学性质, 在前人所做的地质与地球物理研究工作的基础上, 结合各种岩石热力学流变参数, 采用有限元分析方法, 计算了现今构造逆冲之后和中中新世—全新世逆冲过程活跃时两种状态下的深部岩石圈二维温度场和流变结构.模拟计算表明, 南沙海槽前陆盆地地幔热流贡献达60%~70%, 大地热流受深部地幔控制.逆冲推覆构造作用使盆地逆冲推覆带地表热流显著升高了15%~25%, 达到70~75mW/m².盆地沉积层温度在200℃以内, 莫霍面温度420~500℃, 地壳地温梯度25~30℃/km, 盆地热岩石圈厚度为80km左右, 横向上变化幅度不大.南沙海槽前陆盆地深部岩石圈流变性质具有明显的分层特性, 为典型的“三明治”结构.盆地岩石圈综合强度由南沙海槽向逆冲推覆带方向呈下降趋势, 盆地力学岩石圈厚度50km左右, 有效弹性厚度为30~32km.通过模拟盆地深部岩石圈热流变结构, 揭示了盆地深部岩石圈具有强地幔、弱地壳的流变学特征, 表现为高强度块体.同时南沙海域地震活动与深部岩石圈热结构、热活动和岩石圈综合强度密切相关.地壳内热构造活动弱、岩石圈强度大可能是区域地震很少发生的重要原因.
- 南沙海槽 /
- 岩石圈 /
- 温度场 /
- 流变结构 /
- 地震 /
- 有效弹性厚度 /
- 海洋地球物理
Abstract: In order to study the lithospheric thermodynamic properties of Nansha trough foreland basin, we simulate the deep lithosphere temperature field and rheological structure during the thrust faults tectonic activities from Middle Miocene to Holocene and after thrusting (static) in the basin using the finite element method, based on previous studies of geological and geophysical data together with a variety of rock thermodynamic parameters.Simulation results indicate that heat flow contribution from mantle reaches 60%-70% of surface heat flow which is controlled by deep mantle in Nansha trough foreland basin.Thrusting movements increase the surface heat flow in thrust-slip fault belts by 15%-25% to 70-75 mW/m².Our results also show that the temperature of sedimentary layer is less than 200 ℃, while the temperature at Moho varies from 420 to 500 ℃; crust geothermal gradient ranges from 25 to 30 ℃/km.And calculated thickness of thermal lithosphere is about 80 km, which varies slightly laterally.The lithosphere in Nansha waters shows obvious rheological stratification properties, as a typical "sandwich" structure.Horizontally, lithosphere strength decreases in the direction from Nansha trough to thrust belt (NW to SE).The thickness of mechanical lithosphere is about 50 km and the effective elastic thickness ranges from 30 to 32 km.The simulated thermal lithosphere rheological structure also reveals that lithosphere of Nansha basin has rheological characteristics of strong mantle and weak crust, acting as high-strength block.Earthquake activities of Nansha waters are closely related to thermal structure, thermal activity and integrated strength of lithosphere.The weak thermal activity in the crust and high lithosphere strength may be important reasons for rare earthquake occurrence in this area.
- Nansha trough /
- lithosphere /
- temperature field /
- rheological structure /
- earthquakes /
- effective elastic thickness (T_e) /
- marine geophysics

HTML全文

图 1 南沙海槽前陆盆地地理位置、区域构造及热流测点分布(构造和BGR01-07测线根据Franke et al., 2008; Hesse et al., 2010修改)

Fig. 1. Sketch map of tectonic and topographic map of Nansha trough foreland basin in South China Sea

下载: 全尺寸图片幻灯片

图 2 南沙海槽前陆盆地94N05测线的剖面地壳结构

图中数字为岩石圈各层地震P波速度, 单位为km/s, 波速据苏达权等(1996)和Franke et al. (2008)修改

Fig. 2. Crust structure of line 94N05 profile of Nansha trough foreland basin

下载: 全尺寸图片幻灯片

图 3 94N05测线的剖面网格化(剖面位置见图 1)

Fig. 3. Map of grid of line 94N05 profile

下载: 全尺寸图片幻灯片

图 4 岩石圈现今静态(a) 和考虑中中新世—全新世逆冲推覆作用后(b) 的温度场图

图中黑色虚线为热流值; 黑色实线为温度界面, 单位为℃; 白色实线代表逆冲断层; 白色点线是岩石圈层圈界面; 白色箭头代表逆冲断层活动方向

Fig. 4. Temperature fields of deep lithosphere including static (a) and thrusting in process (b)

下载: 全尺寸图片幻灯片

图 5 现今静态的(上) 和逆冲推覆过程中(下) 的岩石圈流变结构

Fig. 5. Rheological structures of deep lithosphere including static (upper) and thrusting in process (lower)

下载: 全尺寸图片幻灯片

表 1 热导率相关参数K₀和C值

Table 1. Parameter values K₀ and C associated with the thermal conductivity

层位	K₀ (W·m^-1K^-1)	C (K^-1)
沉积层	2.0	0
UTK层	3.0	1.5×10^-3
下地壳	3.0	1.5×10^-3
岩石圈上地幔	2.5	-4.0×10^-3
注: UTK层、下地壳、岩石圈上地幔的K₀按文献Liu et al. (2005).

下载: 导出CSV

表 2 岩石圈各层流变参数(据Fernàndez and Ranalli, 1997)

Table 2. Flow law parameters of lithosphere

层位	材料	A (MPa^-n·s^-1)	n	Q (kJ·mol^-1)
上地壳(沉积层)	石英岩	1×10^-6	2.8	150
下地壳	石英闪长岩	3.2×10^-3	3.2	270
岩石圈上地幔	橄榄岩	3.2×10⁴	3.5	535

下载: 导出CSV

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