Evidence for east‐west crustal extension in the Eastern Alps: Implications for the unroofing history of the Tauern window
Evidence for east‐west crustal extension in the Eastern Alps: Implications for the unroofing history of the Tauern window
复制标题
东阿尔卑斯山东西向地壳伸展的证据：对陶恩窗屋顶揭开历史的影响
DOI：
10.1029/tc007i001p00087
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发表时间：
1988
期刊：
影响因子：
4.2
通讯作者：
J. Selverstone
中科院分区：
文献类型：
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作者：
J. Selverstone
陶恩窗西部边界与上覆的奥地利阿尔卑斯山推覆体（奥地利和意大利）之间的接触以在窗去顶的早期阶段形成的构造、岩石学和地质年代学不连续性为标志。在该窗口内，压力-温度-时间路径（J. Selverstone，1985）表明，在逆冲停止后不久（古新世-始新世）发生了显著的韧性减薄。感剪切指标（旋转的斑晶，不对称的眼球和压力阴影，S-C面料）与西倾拉伸线理表明，这种变薄发生在响应顶部到西部的低角度正常剪切变质作用。同样的正向剪切也存在于窗以西的奥阿尔卑斯层序的中生代地层中。然而，在这些岩石中，西向剪切发生在变质热峰之后的低温（<300°C）。结构数据和区域几何学意味着陶恩窗的西端是一个低角度的正断层（布伦纳线），并置脆变形的岩石的奥阿尔卑斯山推覆体对更ductilely变形的岩石从窗口。黑云母K/Ar和Rb/Sr数据表明，Brenner线上的最终运动年龄为中新世。这些数据表明，东阿尔卑斯山脉的东西向伸展有着漫长的历史，影响到地壳的各个层面（早期下地壳的韧性减薄，随后是中地壳到上地壳的低角度正断层）。提出了一个模型，涉及年轻的东西向延伸的位移转移从右行运动上的亚得里亚海线性。在这个模型中，Brenner线和Simplon线，通过类比，可以被认为是拆离断层，它们分别在构造上使Tauern Window和Lepontine热高点失去了顶。
The contact between the western border of the Tauern Window and the overlying Austroalpine nappes (Austria and Italy) is marked by a structural, petrologic, and geochronologic discontinuity that developed in the early stages of unroofing of the window. Within the window, pressure-temperature-time paths (J. Selverstone, 1985) indicate that significant ductile thinning occurred shortly after the cessation of thrusting (Paleocene - Eocene). Sense-of-shear indicators (rotated porphyroblasts, asymmetric augen and pressure shadows, S-C fabrics) associated with a west plunging stretching lineation indicate that this thinning occurred in response to top-to-the-west low-angle normal shear during metamorphism. The same sense of normal shear is present in the Mesozoic members of the Austroalpine sequence west of the window. In these rocks, however, west directed shear occurred at low temperatures (<300°C) after the thermal peak of metamorphism. Structural data and the regional geometry imply that the western end of the Tauern Window is a low-angle normal fault (Brenner Line) that juxtaposed brittlely deformed rocks of the Austroalpine nappes against more ductilely deformed rocks from the window. Biotite K/Ar and Rb/Sr data suggest a Miocene age for final movement on the Brenner Line. These data indicate a prolonged history of east-west extension in the Eastern Alps that affected all crustal levels (early ductile thinning of lower crust followed by mid-to-upper-crustal low-angle normal faulting). A model is presented that relates the young east-west extension to displacement transfer from dextral movement on the Periadriatic Lineament. In this model, the Brenner Line and, by analogy, the Simplon Line can be thought of as detachment faults that tectonically unroofed the Tauern Window and Lepontine thermal highs, respectively.