Intraplate paleostresses reconstructed with calcite twinning and faulting: improved method and application to the eastern Paris Basin (Lorraine, France)
Intraplate paleostresses reconstructed with calcite twinning and faulting: improved method and application to the eastern Paris Basin (Lorraine, France)
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DOI：
10.1016/j.tecto.2004.03.002
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发表时间：
2004-08
期刊：
影响因子：
2.9
通讯作者：
M. Rocher;M. Cushing;F. Lemeille;Y. Lozac'h;J. Angelier
中科院分区：
文献类型：
--
作者：
M. Rocher;M. Cushing;F. Lemeille;Y. Lozac'h;J. Angelier
本研究涉及板内古应力的重建。即使在露头较差的地区，方解石孪生反演也可以提供古应力方向和差异值。然而，现有方法不能很好地适应多相变形情况，并且应力值的计算提供不可靠的估计。对方解石孪晶反演方法和结果处理进行了修改。在新的孪生数据分离过程中，使用整组数据来计算每个张量。考虑了应变硬化孪晶的屈服应力值的可变性。已经利用显示各种晶粒尺寸的样品建立了一阶屈服应力-方解石晶粒尺寸依赖性函数。这种改进的方解石孪生反演方法在巴黎盆地东部（法国洛林）得到应用。在该平台区域，测得的裂缝在所有尺度上均优先走向NE-SW和NW-SE。用断层滑动重建的中新生代古应力序列是复杂的。侏罗纪沉积发生在特提斯裂谷期间。 σ1 连续走向 NNW 和 NNE 的主要走滑阶段归因于第三纪比利牛斯造山作用，随后是渐新世的 WNW 伸展。在局部ENE压缩之后，WNW压缩可能是由于高山晚中新世碰撞造成的。方解石孪晶反演证实了这些构造事件及其演替顺序，并明确了应力轴的方向。使用晶粒尺寸和应变率敏感的屈服应力值，可以以几兆帕的不确定性来估计差应力。它们的范围在 20 至 30 MPa 之间，具体取决于构造事件。使用差异应力值估计的方解石样本的渐新世古深度在结构上是合理的。由此，对原有的方解石孪生反演方法进行了改进。复杂的古应力序列，例如台地地区的古应力序列，可以通过与断层滑移反演相结合来破译。即使可以进行额外的改进，这种方解石孪生反演方法也为确定构造板块中的应力分布开辟了新的方法。
This study deals with the reconstruction of intraplate paleostresses. Calcite twinning inversion provides paleostress directions and differential values, even in poorly outcropping areas. However, existing methods are not well adapted to multi-phase deformation cases, and the calculation of stress values provides unreliable estimates. Modifications were brought to a calcite twinning inverse method and to the processing of results. In a new twin data separation process, the whole set of data is used to calculate each tensor. The variability of yield stress value for twinning with strain hardening is taken into consideration. A first order yield stress-calcite grain size dependence function has been established with a sample showing various grain sizes. This modified method of calcite twinning inversion was applied in the eastern Paris Basin (Lorraine, France). In this platform area, measured fractures are preferentially trending NE–SW and NW–SE at all scales. The Meso-Cenozoic paleostress succession reconstructed with fault slips is complex. Jurassic sedimentation occurred during the Tethys rifting. A mainly strike–slip phase with σ1successively striking NNW and NNE is attributed to the Tertiary Pyrenean orogenesis, and is followed by WNW extension in the Oligocene. After local ENE compression, WNW compression was probably due to the Alpine Late Miocene collision. The calcite twinning inversion has confirmed these tectonic events and their succession order, and the directions of stress axes were specified. Using grain size- and strain rate-sensitive yield stress values, the differential stresses can be estimated with an uncertainty of few MPa. They range between 20 and 30 MPa, depending on the tectonic event. The Oligocene paleodepths of the sampled calcite, estimated using differential stress values, are structurally sensible. Thus, the original calcite twinning inverse method has been improved. Complex paleostress successions such as in platform areas may be deciphered by combination with fault slip inversion. Even if additional improvement is possible, this calcite twinning inverse method opens new ways to determine stress distributions in tectonic plates.