Crustal structure beneath the Jiaodong Peninsula, North China, revealed with a 3D inversion model of magnetotelluric data

AbstractCrustal architecture strongly influences the development and emplacement of mineral zones. In this study, we image the crustal structure beneath a metallogenic belt and its surroundings in the Bayankhongor area of central Mongolia. In this region, an ophiolite belt marks the location of an ancient suture zone, which is presently associated with a reactivated fault system. Nearby, metamorphic and volcanic belts host important mineralization zones and constitute a significant metallogenic belt that includes sources of copper and gold. However, the crustal structure of these features, and their relationships, are poorly studied. We analyze magnetotelluric data acquired across this region and generate three-dimensional electrical resistivity models of the crustal structure, which is found to be locally highly heterogeneous. Because the upper crust (< 25 km) is found to be generally highly resistive (> 1000 Ωm), low-resistivity (< 50 Ωm) features are conspicuous. Anomalous low-resistivity zones are congruent with the suture zone, and ophiolite belt, which is revealed to be a major crustal-scale feature. Furthermore, broadening low-resistivity zones located down-dip from the suture zone suggest that the narrow deformation zone observed at the surface transforms to a wide area in the deeper crust. Other low-resistivity anomalies are spatially associated with the surface expressions of known mineralization zones; thus, their links to deeper crustal structures are imaged. Considering the available evidence, we determine that, in both cases, the low resistivity can be explained by hydrothermal alteration along fossil fluid pathways. This illustrates the pivotal role that crustal fluids play in diverse geological processes, and highlights their inherent link in a unified system, which has implications for models of mineral genesis and emplacement. The results demonstrate that the crustal architecture—including the major crustal boundary—acts as a first‐order control on the location of the metallogenic belt.

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Detailed crustal structure of the North China and its implication for seismicity

Journal of Asian Earth Sciences ◽

10.1016/j.jseaes.2013.11.021 ◽

2014 ◽

Vol 81 ◽

pp. 53-64 ◽

Cited By ~ 14

Author(s):

Wenliang Jiang ◽

Xin Wang ◽

Tian Tian ◽

Jingfa Zhang ◽

Donglei Wang

Keyword(s):

Crustal Structure ◽

North China ◽

The North

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Contrasting Lu–Hf isotopes in zircon from Precambrian metamorphic rocks in the Jiaodong Peninsula: Constraints on the tectonic suture between North China and South China

Precambrian Research ◽

10.1016/j.precamres.2014.01.006 ◽

2014 ◽

Vol 245 ◽

pp. 29-50 ◽

Cited By ~ 27

Author(s):

Shao-Bing Zhang ◽

Jun Tang ◽

Yong-Fei Zheng

Keyword(s):

South China ◽

North China ◽

Hf Isotopes ◽

Metamorphic Rocks ◽

Jiaodong Peninsula

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Geochemical Evidence for Thickening and Thinning of Lower Crust beneath the Jiaodong Peninsula: Implications for Late Mesozoic Destruction of the Eastern North China Craton

Lithosphere ◽

10.2113/2020/8831664 ◽

2020 ◽

Vol 2020 (1) ◽

Author(s):

YaYun Liang ◽

Wenhui Guo ◽

Yao Ma ◽

Enquan Zhao

Keyword(s):

Continental Crust ◽

Early Cretaceous ◽

North China Craton ◽

Late Jurassic ◽

North China ◽

Temporal Variations ◽

Late Mesozoic ◽

Jiaodong Peninsula ◽

Intrusive Rocks ◽

Subducting Slab

Abstract The eastern North China Craton (NCC) has been recognised as undergoing cratonic destruction during the Mesozoic; however, the mechanism of its destruction is still unclear. The main difference between the proposed models is whether the lower continental crust (LCC) underwent thinning. In this study, we conducted comprehensive analyses of Late Mesozoic felsic intrusive rocks, including Late Jurassic granites (166–146 Ma), Early Cretaceous granodiorites (136–123 Ma), and latest Early Cretaceous granites (123–108 Ma) from the Jiaodong Peninsula, located on the southeastern margin of the NCC. These rocks allowed us to investigate variations in the LCC thickness in this region and to further discuss the destruction mechanism of the eastern NCC. Here, temporal variations in crustal thickness can be tracked using whole-rock La/Yb ratios of the felsic intrusive rocks. Our study shows that the continental crust in the eastern NCC thickened during the Late Jurassic (>40 km) due to compression and the westward subduction of the Palaeo-Pacific Ocean lithosphere beneath the NCC since the Early Jurassic. The continental crust further thickened during the Early Cretaceous, caused by the steepening of the subducting slab after ~144 Ma that produced crustal underplating of mantle-derived melts in an extensional setting. However, the continental crust thinned (20–40 km) during the latest Early Cretaceous, caused by the rollback of the subducting slab after ~123 Ma. The geochemical compositions of three stages of felsic intrusions also suggest that the regional tectonic stress that affects the eastern NCC altered from a compressional to an intraplate extensional environment after ~144 Ma. Thus, the Late Mesozoic destruction of the eastern NCC and its accompanying magmatism were controlled by prolonged thermomechanical-chemical erosion due to low-angle subduction, steepening, and rollback of the Palaeo-Pacific Oceanic lithosphere.

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Constraints on the Structure of the Border Ranges Fault System, Kenai Peninsula, Alaska from the Preliminary Results of the 3D Inversion Model of Gravity Data

ASEG Extended Abstracts ◽

10.1071/aseg2013ab367 ◽

2013 ◽

Vol 2013 (1) ◽

pp. 1-3

Author(s):

Niti Mankhemthong ◽

Diane I. Doser ◽

Mark Baker ◽

Rolando Cardenas

Keyword(s):

Gravity Data ◽

Fault System ◽

3D Inversion ◽

Kenai Peninsula ◽

Preliminary Results ◽

Inversion Model

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Constructing piecewise-constant models in multidimensional minimum-structure inversions

Geophysics ◽

10.1190/1.2816650 ◽

2008 ◽

Vol 73 (1) ◽

pp. K1-K9 ◽

Cited By ~ 117

Author(s):

Colin G. Farquharson

Keyword(s):

Gravity Data ◽

Model Structure ◽

Iteratively Reweighted Least Squares ◽

3D Inversion ◽

Magnetotelluric Data ◽

2D Inversion ◽

Piecewise Constant ◽

Text Type ◽

Current Minimum ◽

Modified Algorithm

A modification of the typical minimum-structure inver-sion algorithm is presented that generates blocky, piecewise-constant earth models. Such models are often more consistent with our real or perceived knowledge of the subsurface than the fuzzy, smeared-out models produced by current minimum-structure inversions. The modified algorithm uses [Formula: see text]-type measures in the measure of model structure instead of the traditional sum-of-squares, or [Formula: see text], measure. An iteratively reweighted least-squares procedure is used to deal with the nonlinearity introduced by the non-[Formula: see text] measure. Also, and of note here, diagonal finite differences are included in the measure of model structure. This enables dipping interfaces to be formed. The modified algorithm retains the benefits of the minimum-structure style of inversion — namely, reliability, robustness, and minimal artifacts in the constructed model. Two examples are given: the 2D inversion of synthetic magnetotelluric data and the 3D inversion of gravity data from the Ovoid deposit, Voisey’s Bay, Labrador.

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