Abstract We present a study on the mylonites exposed in the Cirella area along the Tyrrhenian coast of northern Calabria (southern Italy), in order to understand the role of ductile and brittle deformation on the exhumation process of these rocks. The analyzed shear zone is located in the footwall of a regional tectonic contact between metaophiolites (Ligurian Complex) on the top, and the continental Lungro-Verbicaro Unit (Adria plate) at the bottom. The latter consists of a metasedimentary succession with Triassic shallow-water carbonates at the base of it, evolving upward to Jurassic-lower Miocene slope to deep basin carbonates and foredeep siliciclastic rocks. Both oceanic and continental successions are characterized by high-pressure and low-temperature (HP-LT) metamorphism. The analyzed mylonites show different degrees of strain, ranging from protomylonites to ultramylonites, the latter characterized by well-marked foliation and stretching lineations. Several micro- and mesoscale progressive deformation structures, including two fold sets, S-C’ structures are present in these rocks, and a late oblique foliation, indicating a NW sense of shear. A successive shortening stage produced thrust faults and related folds, indicating a tectonic transport toward SE. We associate the mylonitic deformation with the activity of the overlying detachment fault, which is responsible for the synorogenic exhumation of the Lungro-Verbicaro Unit during the Miocene time. However, the ductile strain, recorded by the studied mylonites, accounted for a small displacement during the exhumation of this tectonic slice. In fact, the calculated displacement achieved by the Lungro-Verbicaro Unit, during exhumation, is much larger than the one estimated considering only the ductile zones activity. This evidence suggests that, synchronously with ductile strain, brittle deformation occurred along the detachment fault located at the top of the thrust sheet. In addition, a severe erosion due to the tectonic exhumation of the HP-LT rocks (in the late Miocene) produced a large amount of clastic sediment that filled the extensional basins widespread in northern Calabria.

中文翻译：

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HP-LT 岩石同生折返过程中的脆性与韧性应变：来自 Lungro-Verbicaro Unit 糜棱岩（意大利卡拉布里亚北部）的一个例子

摘要 我们对卡拉布里亚北部（意大利南部）第勒尼安海岸的 Cirella 地区出露的糜棱岩进行了研究，以了解韧性和脆性变形对这些岩石折返过程的作用。分析的剪切带位于顶部变蛇绿岩（利古里亚杂岩）与底部大陆 Lungro-Verbicaro 单元（亚德里亚板块）之间的区域构造接触的下盘。后者由以三叠系浅水碳酸盐岩为基础的变沉积层序组成，向上演化至侏罗系-下中新世斜坡至深盆碳酸盐岩和前深部硅质碎屑岩。大洋和大陆序列都具有高压和低温 (HP-LT) 变质作用。分析的糜棱岩表现出不同程度的应变，范围从原糜棱岩到超糜棱岩，后者的特征是明显的叶理和伸展的纹路。几个微尺度和中尺度渐进变形结构，包括两个褶皱组，这些岩石中存在 S-C' 结构，以及晚期斜叶理，表明 NW 剪切感。连续的缩短阶段产生了逆冲断层和相关的褶皱，表明构造运动向东南方向移动。我们将糜棱质变形与上覆分离断层的活动联系起来，后者是中新世时期 Lungro-Verbicaro 单元的同步剥脱的原因。然而，所研究的糜棱岩记录的韧性应变解释了该构造切片挖掘过程中的小位移。事实上，Lungro-Verbicaro Unit 实现的计算位移，在挖掘过程中，比仅考虑韧性区活动所估计的要大得多。这一证据表明，与延性应变同步，沿位于逆冲片顶部的脱离断层发生脆性变形。此外，由于 HP-LT 岩石（中新世晚期）的构造剥蚀造成的严重侵蚀产生了大量碎屑沉积物，这些沉积物充满了卡拉布里亚北部普遍存在的伸展盆地。