Time constraints on the Early Palaeozoic docking of the Precordillera, central Argentina
Time constraints on the Early Palaeozoic docking of the Precordillera, central Argentina
复制标题
阿根廷中部普雷迪勒拉早古生代对接的时间限制
DOI：
--
复制
发表时间：
1998
期刊：
影响因子：
--
通讯作者：
G. Vujovich
中科院分区：
文献类型：
--
作者：
V. Ramos;R. D. Dallmeyer;G. Vujovich
本文测定了早古生代前古生代以东的Sierras Pampeas西部帕洛山基岩中制备的白云母和角闪石精矿的40Ar/39Ar增量释放年龄。基底主要以蛇绿岩、正长片麻岩和片岩等可变变质单元为代表。前人对基底岩浆和变质锆石进行了U-Pb、Rb-Sr、K-Ar和40Ar/39Ar定年，表明其时代为中元古代。40Ar/39Ar坪年龄制约了与相邻前陆盆地构造不连续发育有关的一系列韧性变形事件。假设了以下变形事件：(1)前地台与冈瓦那的碰撞和溺水(470-460 Ma)；(2)由于冈瓦那边缘的构造载荷而与正断层有关的挠曲伸展；(3)前陆盆地的发展(450-430 Ma)。这些中奥陶世-志留纪事件与冈瓦那边缘多个奇异的早古生代地体碰撞有关。Punta Negra前陆盆地在早-中泥盆世(410-380 Ma)进一步向西发展，并与前记录时代西缘奇列尼亚地体开始对接有关。
Abstract 40Ar/39Ar incremental-release ages have been determined for muscovite and hornblende concentrates prepared from basement rocks of the Sierra de Pie de Palo, in the western Sierras Pampeanas, east of the Early Palaeozoic Precordillera. The basement is mainly represented by variably metamorphosed units, including ophiolites, orthogneisses and schists. Previous U-Pb, Rb-Sr, K-Ar, and 40Ar/39Ar dating of magmatic and metamorphic zircons from the basement has indicated a Middle Proterozoic age. The 40Ar/39Ar plateau ages constrain a series of ductile deformational events that are correlated with development of structural discontinuities in adjacent foreland basins. The following deformational events are postulated: (1) initiation of collision and drowning of the Precordillera platform against Gondwana (470–460 Ma); (2) flexural extension associated with normal faulting due to tectonic loading of the Gondwana margin; and (3) development of a foreland basin (450–430 Ma). These Mid-Ordovician-Silurian events were related to collision of several exotic Early Palaeozoic terranes along the Gondwana margin. The Punta Negra foreland basin developed further west during Early to Mid-Devonian (410–380 Ma) times, and was linked to the beginning of the docking of the Chilenia terrane along the western margin of the Precordillera.