The Pampean flat-slab of the Central Andes
The Pampean flat-slab of the Central Andes
复制标题
DOI：
10.1016/s0895-9811(02)00006-8
复制
发表时间：
2002-04
影响因子：
1.8
通讯作者：
V. Ramos;E. Cristallini;D. Pérez
中科院分区：
文献类型：
--
作者：
V. Ramos;E. Cristallini;D. Pérez
晚新生代阿根廷-智利帕森斯板块（27°00′-33 ° 30 ′S）的安第斯变形为研究活动会聚边缘的平坦俯冲造山作用提供了一个难得的机会。在这些纬度上，来自海洋地貌结构的约束表明，纳斯卡板块的胡安费尔南德斯海岭与智利海沟的碰撞从大约1000年开始由北向南传播。18、我的十一马。在这一地区，新生代的构造导致了主山脉和前山脉、Cuyo Precordillera以及东部前陆地区相关的Sierras Pampeanas的发展。对南纬27 °至33°之间横跨Sierras Pampeanas的不同构造断面的分析表明，Sierra de Pampeanas（南纬27°）的基底块体隆升开始于7.6至6 Ma，Sierra de Famatina（南纬29 °）为4.5至4.19Ma，Sierra de Pocho（南纬31°）为5.5至4.7Ma，而Sierra de Pocho（南纬31°）约为5.5至4.7Ma。2.6Ma在Sierra de San Luis（33°S）。不稳定期受同造山期矿床年龄、磷灰石裂变径迹数据和明矾石氢同位素（如果有的话）的制约。将这些时间限制与岩浆活动向前陆的迁移和扩展进行了比较。这两个数据集的关系表明，在大约4-2.6Ma的停留时间之后，岩浆活动与导致基底块体隆起的地壳破裂之间存在惊人的一致性。地壳的热弱化与向东迁移的弧岩浆作用，以提高脆韧性地下沉降，从而导致厚皮基底隆起的Sierras Pampeanas。Sierras Pampeanas的演变与南纬33°的主要安第斯山脉的演变有关。主科迪勒拉薄皮和厚皮褶皱冲断带的主要变形阶段和隆升发生在20 ~ 8.6Ma之间。在16 ~ 15.8Ma之间，弧火山活动向东迁移。这种扩张伴随着变形和隆起，形成了前陆盆地。俯冲带变浅后不久，造山缩短和盆地形成之后，火山前缘迁移到前陆。逆冲前缘的传播速率从早期（15- 9 Ma）的2.5mm/a加速到变浅中期（9- 6 Ma）和晚期（5- 2 Ma）的13.3和13.7mm/a。前科迪勒拉的隆起与主科迪勒拉变形的最后阶段在9 Ma时重叠。这一时间也受到前陆沉积物的磁性地层学研究的限制，这些研究记录了弧岩浆活动扩展到Sierras Pampeanas的同时沉降速率的快速增加，介于9.5和6.4Ma之间。逆冲前缘的快速扩展和弧岩浆活动的迁移发生在该纬度胡安费尔南德斯海岭碰撞11 Ma之后的2 m.从2.6Ma到现在，在南纬33°附近，通过先存正断层的构造反转和Sierras Pampeanas的基底隆起，发生了前心脏地带的隆起。新构造研究以及全球定位系统的测量结果表明，在前科迪勒拉的逆冲前缘以及Sierras Pampeanas都有活跃的变形。主山脉的岩浆活动大约在8.6Ma结束，而Sierras Pampeanas则在1.9Ma结束。最后一次与俯冲有关的火山活动发生在海沟以东750公里处。沿着四个不同的断面进行的分析表明，岩浆弧的向东传播，形成新的脆-韧性过渡带作为一个功能的热输入，造山变形之间的密切关系。不稳定和...
Late Cenozoic Andean deformation in the Pampean segment of Argentina and Chile (27°00′–33°30′S) provides an exceptional opportunity to study the orogenic effects of flat subduction in an active convergent margin. At these latitudes, constraints derived from oceanic geomorphic structures indicate that collision of the Juan Fernandez Ridge in the Nazca plate with the Chilean trench propagated from north to south from ca. 18 to ca. 11Ma. In this region, Cenozoic tectonics have resulted in the development of the Principal and Frontal Cordilleras, the Cuyo Precordillera, and the associated Sierras Pampeanas in the eastward foreland region. The analyses of different structural transects across the Sierras Pampeanas between 27 and 33°S latitudes show a southward diachronic beginning of basement block uplift from 7.6 to 6Ma in the Sierra de Aconquija (27°S), 4.5 to 4.19Ma at Sierra de Famatina (29°S), 5.5 to 4.7Ma at Sierra de Pocho (31°S), and ca. 2.6Ma at Sierra de San Luis (33°S). Uplift times are constrained by the age of synorogenic deposits, fission-track data on apatite, and hydrogen isotopes in alunite, where available. These time constraints are compared with the migration and expansion of the magmatic activity into the foreland. The relation of these two data sets shows a striking coincidence, after a residence time of approximately 4–2.6Ma, between magmatic activity and failure of the crust that resulted in basement block uplift. Thermal weakening of the crust associated with eastward migration of arc magmatism acted to elevate brittle–ductile subsurface décollments, thus leading to thick-skinned basement uplift of the Sierras Pampeanas. The evolution of the Sierras Pampeanas is linked to that of the main Andes at 33°S latitude. The main deformation phases and uplift of the thin- and thick-skinned fold and thrust belts of Principal Cordillera occurred between 20 and 8.6Ma. Arc volcanism migrated eastward at this latitude between 16 and 15.8Ma. This expansion was accompanied by deformation and uplift with the development of a foreland basin. Soon after the shallowing of the subduction zone, orogenic shortening and basin formation were followed by a migration of the volcanic front to the foreland. Propagation rates of the thrust front from 2.5mm/a in the early stage (15–9Ma) accelerated to 13.3 and 13.7mm/a during the middle (9–6Ma) and late (5–2Ma) stages of shallowing. Uplift of the Frontal Cordillera overlapped the last stages of Principal Cordillera deformation at 9Ma. This time is also constrained by magnetostratigraphic studies of the foreland deposits that record a rapid increase in subsidence rates at the same time that arc magmatism expanded to the Sierras Pampeanas, between 9.5 and 6.4Ma. This rapid propagation of the thrust front and migration of the arc magmatism occurred 2 m.yr later than the 11Ma collision of the Juan Fernandez Ridge at this latitude. Uplift of the Precordillera by tectonic inversion of pre-existing normal faults and basement uplifts of the Sierras Pampeanas in the vicinity of 33°S occurred from 2.6Ma to the present. Neotectonic studies, as well as GPS measurements, indicate active deformation in the thrust front of the Precordillera, as well as in the Sierras Pampeanas. Magmatic activity ended in the Principal Cordillera at approximately 8.6Ma and in the Sierras Pampeanas at 1.9Ma. The last subduction-related volcanism occurred more than 750km east of the trench. Analyses performed along four different transects show close relations between eastward propagation of the magmatic arc, formation of new brittle–ductile transition zones as a function of heat input, and orogenic deformation. Uplift and …