A Thermo‐Compositional Model of the Cratonic Lithosphere of South America
A Thermo‐Compositional Model of the Cratonic Lithosphere of South America
复制标题
DOI：
10.1029/2020gc009307
复制
发表时间：
2021-01
期刊：
影响因子：
3.7
通讯作者：
N. Finger;M. Kaban;M. Tesauro;C. Haeger;W. Mooney;Maik Thomas
中科院分区：
文献类型：
--
作者：
N. Finger;M. Kaban;M. Tesauro;C. Haeger;W. Mooney;Maik Thomas
最近出现了新的南美洲地壳和上地幔地震资料，并以前所未有的分辨率描述了其深部结构。在这里，地震数据与重力数据和矿物物理约束相结合，建立了南美岩石圈和亚岩石圈上地幔的温度、成分和密度的自一致模型。建立了一个新的地壳结构模型，包括沉积物和平均地壳密度和莫霍剖面的深度。利用该地壳模型对重力场进行校正，得到残差地形。然后，通过重力和残余地形联合反演的迭代过程，对基于地震层析成像和矿物物理的初始温度模型进行改进。结果显示，在亚马逊河、<s:1>弗朗西斯科河和帕拉那帕内玛克拉通的大部分地区都存在深层克拉通根，但在拉普拉塔河和Parnaíba克拉通中却没有。这些克拉通可能从未形成岩石圈根，或在随后的构造事件中恢复活力。我们假设西北亚马逊克拉通的根部是由圭亚那高地下的热地幔物质上涌而移走的。<s:1>奥弗朗西斯科克拉通下方明显的温度和密度异常似乎与帕那帕内玛克拉通的温度和密度异常有关，这可能表明其根部向西移动。帕那帕内玛克拉通南部的枯竭可能是以前更大的克拉通的残余物，由于热地幔物质的上涌而恢复活力，导致帕那帕纳帕内玛<s:1>洪水玄武岩的就位。
New seismic data on the crust and upper mantle of South America have recently become available and describe its deep structure with unprecedented resolution. Here, seismic data are combined with gravity data and mineral physics constraints to develop self‐consistent models of the temperature, composition, and density of the South American lithospheric and sub‐lithospheric upper mantle. A new model of the crustal structure was developed, including sediment and average crustal density and depth to the Moho. This crustal model was used to correct the gravity field and obtain the residual topography. Then, an initial temperature model, derived from seismic tomography and mineral physics, was improved through an iterative process based on the joint inversion of gravity and residual topography. The results reveal deep cratonic roots present under wide parts of the Amazon, São Francisco, and Paranapanema Cratons, but not under the Rio de la Plata and Parnaíba Cratons. These cratons probably never developed lithospheric roots or were rejuvenated during subsequent tectonic events. We hypothesize that the root of the northwestern Amazon craton was removed by upwelling of hot mantle material under the Guyana highlands. Temperature and density anomalies evident beneath the São Francisco Craton appear to be connected with those of the Paranapanema Craton, which could indicate a westward shift of its root. Depletion south of the Paranapanema Craton probably denotes remnants of a previously larger craton that was rejuvenated by the upwelling of hot mantle material leading to emplacement of the Paraná Flood Basalts.