Evolving temperature field in a fossil subduction channel during the transition from subduction to collision (Tauern Window, Eastern Alps)
Evolving temperature field in a fossil subduction channel during the transition from subduction to collision (Tauern Window, Eastern Alps)
复制标题
从俯冲到碰撞过渡期间化石俯冲通道中温度场的演变（陶恩窗，东阿尔卑斯山）
DOI：
10.1111/jmg.12572
复制
发表时间：
2020
影响因子：
3.4
通讯作者：
T. John
中科院分区：
文献类型：
--
作者：
Philip Groß;J. Pleuger;M. Handy;Marisa Germer;T. John
我们研究了暴露在中央陶恩窗（东阿尔卑斯山）的Penninic单元中的古俯冲通道的三维热结构的演化。结构和岩石学观察显示，在高P条件下（~2 GPa）形成的幅度约为20 km的鞘褶皱。褶皱是一种复合结构，它将来自特提斯阿尔卑斯洋的蛇绿推覆体的逆冲断层等倾折叠到远侧欧洲大陆边缘的一个单元上，也受到高P条件的影响。这个结构组合被保存在陶恩窗两端的两个较年轻的圆顶之间。穹隆使T主导的巴罗变质作用的等梯度线变形，而巴罗变质作用本身覆盖了部分保存在鞘褶皱中的高P变质作用。利用碳质材料的拉曼光谱（RSCM），我们能够区分与原始俯冲变质作用相关的峰温域和与后期温度主导（巴罗）变质作用相关的域。在Barrovian域的RSCM温度的分布表明，随着距离热穹中心的距离增加，峰值温度的横向和垂直下降。这代表了古温度的下降，与以前的研究一致。然而，我们观察到相反的古温度趋势在鞘褶皱的下肢，即上升。我们将这种倒置的古温度域解释为俯冲相关温度场的遗迹。朝向鞘褶的上部边缘的中央部分，RSCM温度增加到最高约520°C。在鞘褶皱的上盘中进一步向上剖分，古峰值温度降低到与叠加的巴罗变质作用的峰值温度难以区分的程度。俯冲相关变质作用的峰值温度等值线大致平行于褶皱推覆接触面和岩性分层。轮廓向褶皱的北方、西部和东部靠近，导致横截面呈眼状同心图案。因此，温度轮廓几何形状模拟折叠几何形状本身，表明这些轮廓也以鞘管样方式折叠。我们认为，这种鞘状构造是两阶段过程的结果，反映了俯冲带推覆体形成方式从逆冲推覆到褶皱推覆体形成的变化。首先，热的海洋推覆体逆冲到较冷的大陆推覆体上，产生了反向的峰值热梯度。第二，这种复合推覆构造的鞘褶皱与先前建立的折返过程中的峰值温度模式一起。这种模式之所以得以保存，是因为在退变质作用期间温度降低，并且在后期巴罗叠加期间保持低于俯冲相关的峰值温度。褶皱在俯冲通道中以类似底辟的运动学上升。
We investigate the evolution of the three‐dimensional thermal structure of a palaeo‐subduction channel exposed in the Penninic units of the central Tauern Window (Eastern Alps). Structural and petrological observations reveal a sheath fold with an amplitude of some 20 km that formed under high‐P conditions (~2 GPa). The fold is a composite structure that isoclinally folded the thrust of an ophiolitic nappe derived from Alpine Tethys Ocean onto a unit of the distal European continental margin, also affected by the high‐P conditions. This structural assemblage is preserved between two younger domes at either end of the Tauern Window. The domes deform isograds of the T‐dominated Barrovian metamorphism that itself overprints the high‐P metamorphism partly preserved in the sheath fold. Using Raman spectroscopy on carbonaceous material (RSCM), we are able to distinguish peak‐temperature domains related to the original subduction metamorphism from domains associated with the later temperature‐dominated (Barrovian) metamorphism. The distribution of RSCM temperatures in the Barrovian domain indicates a lateral and vertical decrease of peak temperature with increasing distance from the centres of the thermal domes. This represents a downward increase of palaeo‐temperature, in line with previous studies. However, we observe the opposite palaeo‐temperature trend in the lower limb of the sheath fold, namely an upward increase. We interpret this inverted palaeo‐temperature domain as the relic of a subduction‐related temperature field. Towards the central part of the sheath fold's upper limb, RSCM temperatures increase to a maximum of ~520°C. Further upsection in the hangingwall of the sheath fold, palaeo‐peak temperatures decrease to where they are indistinguishable from the peak temperatures of the overprinting Barrovian metamorphism. Peak‐temperature contours of the subduction‐related metamorphism are oriented roughly parallel to the folded nappe contacts and lithological layering. The contours close towards the northern, western and eastern parts of the fold, resulting in an eye‐shaped, concentric pattern in cross‐section. The temperature contour geometry therefore mimics the fold geometry itself, indicating that these contours were also folded in a sheath‐like manner. We propose that this sheath‐like pattern is the result of a two‐stage process that reflects a change of the mode of nappe formation in the subduction zone from thrusting to fold nappe formation. First, thrusting of a hot oceanic nappe onto a colder continental nappe created an inverted peak‐thermal gradient. Second, sheath folding of this composite nappe structure together with the previously established peak‐temperature pattern during exhumation. This pattern was preserved because temperatures decreased during retrograde exhumation metamorphism and remained less than the subduction‐related peak temperatures during the later Barrovian overprint. The fold ascended with diapir‐like kinematics in the subduction channel.
登录
查看更多内容
陶恩之窗（奥地利东阿尔卑斯山）：新的构造图，包含横截面和构造变质综合
影响因子：
3.1
作者：
Schmid;Scharf;Rosenberg
通讯作者：
Rosenberg
影响因子：
3.8
作者：
N. K. Lünsdorf;I. Dunkl;B. Schmidt;G. Rantitsch;H. Eynatten
通讯作者：
N. K. Lünsdorf;I. Dunkl;B. Schmidt;G. Rantitsch;H. Eynatten
影响因子：
2.9
作者：
S. Favaro;R. Schuster;M. Handy;A. Scharf;G. Pestal
通讯作者：
S. Favaro;R. Schuster;M. Handy;A. Scharf;G. Pestal
影响因子：
2.9
作者：
A. Scharf;M. Handy;S. Schmid;S. Favaro;M. Sudo;R. Schuster;K. Hammerschmidt
通讯作者：
A. Scharf;M. Handy;S. Schmid;S. Favaro;M. Sudo;R. Schuster;K. Hammerschmidt
由吸积、俯冲和碰撞引起的多相变质作用的峰值温度模式（东陶恩窗，欧洲阿尔卑斯山）——碳质材料拉曼显微光谱研究（RSCM）
影响因子：
3.4
作者：
Scharf;Ziemann;Schmid
通讯作者：
Schmid