Exhumation and uplift of the Sierras Pampeanas: preliminary implications from K-Ar fault gouge dating and low-T thermochronology in the Sierra de Comechingones (Argentina)
Exhumation and uplift of the Sierras Pampeanas: preliminary implications from K-Ar fault gouge dating and low-T thermochronology in the Sierra de Comechingones (Argentina)
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DOI：
10.1007/s00531-010-0608-0
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发表时间：
2011-04-01
影响因子：
2.3
通讯作者：
Siegesmund, Siegfried
中科院分区：
文献类型：
--
作者：
Loebens, Stefan;Bense, Frithjof A.;Siegesmund, Siegfried
阿根廷中部和西北部的Sierras Pampeanas在南纬27 A度和33 A度之间构成了一个独特的地貌构造特征。该区最后阶段的隆升和变形与纳斯卡板块向南美板块下的安第斯板块俯冲密切相关。K-Ar断层泥测年和低温热年代学沿着两个断面内的Comechingones山脉揭示了一个最小的年龄约340 Ma的脆性变形的开始，非常低的折返率，自晚古生代的时间，以及总折返约2.3公里，自晚白垩世。圣路易斯火山带火山岩新的Ar-Ar年龄（7.54-1.91 Ma）支持了板块岩浆前缘的东向传播，证实了该地区板块变形的起始时间为11.2 Ma。虽然低温热年代学并没有明确限制安第斯隆起的信号，但可以理解的是，目前与Comechingones山脉有关的结构起伏是在两个断层壁（约80-70 Ma）的折返之后实现的。
The Sierras Pampeanas in central and north-western Argentina constitute a distinct morphotectonic feature between 27A degrees S and 33A degrees S. The last stage of uplift and deformation in this area are interpreted to be closely related to the Andean flat-slab subduction of the Nazca plate beneath the South American plate. K-Ar fault gouge dating and low-temperature thermochronology along two transects within the Sierra de Comechingones reveal a minimum age for the onset of brittle deformation about 340 Ma, very low exhumation rates since Late Paleozoic time, as well as a total exhumation of about 2.3 km since the Late Cretaceous. New Ar-Ar ages (7.54-1.91 Ma) of volcanic rocks from the San Luis volcanic belt support the eastward propagation of the flat-slab magmatic front, confirming the onset of flat-slab related deformation in this region at 11.2 Ma. Although low-temperature thermochronology does not clearly constrain the signal of the Andean uplift, it is understood that the current structural relief related to the Comechingones range has been achieved after the exhumation of both fault walls (circa 80-70 Ma).