We combine structural analysis of fractures with 22 U–Pb dates measured in fracture-filling carbonate cements from bed-parallel fibrous calcite veins (beef), conjugated veins and faults within the Vaca Muerta Formation along the Andean fold and thrust belt in the Neuquén Basin. The measured ages constrain accurately the relationships between overpressures caused by hydrocarbon generation and Andean compression as mechanisms for natural fracturing and vein formation.

Two generations of fibres have been identified in beef. The first one, consists of dark fibres from the inner zones, which are perpendicular to bedding and contain abundant cone-in-cone structures and hydrocarbon inclusions. U–Pb dating of these fibres yielded Early to Late Cretaceous ages from 116.7 ± 17.7 to 78.8 ± 10.2 Ma. The second generation of fibres corresponds to the outer zones and consists of white fibres oblique to bedding, indicating growth during layer-parallel shortening.

Bed-perpendicular veins cutting beef yielded Late Cretaceous-late Palaeocene dates from 72.8 ± 22.4 to 60.9 ± 10.4 Ma. Eocene ages from 52.0 ± 2.9 to 42.2 ± 18.9 Ma were measured in bed-parallel slip surfaces and reverse and strike-slip faults, whereas Miocene dates from 13.9 ± 2.6 to 6.2 ± 1.1 Ma were measured in E-W calcite veins.

U–Pb dating of veins, structural analysis of fractures and subsidence curves, indicate that beef inner zones formed in the oil window during burial of the Neuquén basin, and that tectonic stresses could enhance their formation. Beef outer zones and bed-perpendicular veins formed during E-W Late Cretaceous-late Palaeocene layer-parallel shortening. Contrarily, late Palaeocene-late Eocene bed-parallel slip surfaces and faults and Miocene E-W veins formed during NE-SW and E-W syn-to post-folding deformation, respectively. In both cases, syn-to post-folding compression occurred synchronously with forelandward migration of magmatic activity attributed to flat subduction of the Pacific slab beneath the Andes.

我们将裂缝的结构分析与内乌肯盆地沿安第斯褶皱和逆冲带的 Vaca Muerta 组内平行纤维方解石脉（牛肉）、共轭脉和断层的裂缝填充碳酸盐胶结物中测量的 22 U-Pb 日期相结合. 测得的年龄准确地限制了由生烃引起的超压与作为自然压裂和脉形成机制的安第斯压缩之间的关系。

已经在牛肉中鉴定出两代纤维。第一个由来自内部区域的暗纤维组成，它们垂直于层理并包含丰富的锥中锥结构和碳氢化合物包裹体。这些纤维的 U-Pb 测年产生了早到晚白垩世的年龄从 116.7 ± 17.7 到 78.8 ± 10.2 Ma。第二代纤维对应于外部区域，由倾斜于层理的白色纤维组成，表明在平行层缩短期间生长。

切割牛肉的床垂直脉产生晚白垩世-晚古新世的年代为 72.8 ± 22.4 至 60.9 ± 10.4 Ma。始新世年龄从 52.0 ± 2.9 到 42.2 ± 18.9 Ma 在平行床滑动面和反向和走滑断层中测量，而中新世年龄从 13.9 ± 2.6 到 6.2 ± 1.1 Ma 在 EW 方解石脉中测量。

脉的 U-Pb 测年、裂缝和沉降曲线的结构分析表明，在内乌肯盆地埋藏期间在油窗口中形成了牛肉内带，并且构造应力可以增强它们的形成。在 EW 晚白垩世-晚古新世平行层缩短期间形成的牛肉外带和床垂直脉。相反，晚古新世-晚始新世地层平行滑动面和断层以及中新世东西脉分别在 NE-SW 和 EW 同步到折叠后变形过程中形成。在这两种情况下，由于安第斯山脉下方太平洋板块的平坦俯冲，岩浆活动的前陆迁移同时发生了同步到折叠后的压缩。