Magmatic Origins of Extensional Structures in Tempe Terra, Mars

Abstract Numerous graben features transect the Tempe Terra plateau in the northeastern Tharsis Rise, Mars, making it one of the most heavily structured regions of Tharsis. The origin of the complex fault geometries, generated over three distinct stages of tectonic activity, is poorly understood. This work distinguishes between Tempe Terra structures of local and regional origin, to isolate regional deformation patterns related to the general development of the Tharsis Rise from the patterns due to effects of local stress mechanisms. Comparison of structural observations to predicted deformation patterns from different drivers of graben formation in the Martian crust demonstrates the important role of magmatic activity at a variety of scales in driving tectonism in Tempe Terra. Noachian (Stage 1) faulting resulted from local magmatic underplating and associated heating and uplift, which formed part of an incipient stage of widespread Tharsis volcanism that predated development of the main Tharsis Rise. Early Hesperian (Stage 2) faults reflect the interaction of regional stresses from growth of Tharsis with magmatic activity highly localized along the Tharsis Montes Axial Trend—a linear volcanotectonic trendline including the alignment of the Tharsis Montes volcanoes. Early–Late Hesperian (Stage 3) faulting resulted from a series of dyke swarms from a Tharsis-centered plume, which propagated in a regional stress field generated by growth of the Tharsis Rise. As only Stage 2 NNE faults and Stage 3 ENE faults are linked to regional, Tharsis-related stresses, other observed Tempe Terra fault trends can be excluded when evaluating models of Tharsis's tectonic evolution. Key Points The 3 stages of Tempe Terra's tectonic activity have different origins, with local and regional scale magmatic sources driving deformation Magmatectonic activity began in Tempe Terra prior to development of the Tharsis Rise topographic bulge and associated major volcanoes Only 2 Tempe Terra fault trends (NNE and ENE), both Hesperian age, represent stresses related to the growth of the Tharsis Rise Plain Language Summary Tharsis is the largest volcanic province on Mars and its formation was a major driver of the deformation we see at the surface. Tectonic structures that record this deformation are therefore used to understand how and when Tharsis formed. However, local structural patterns may obscure regional trends associated with Tharsis-forming stresses, complicating our ability to assess models for how Tharsis developed. As such, distinguishing between faults with local and regional origins is essential. We study the Tempe Terra region in northeastern Tharsis to determine the origin of the region's extensive faulting, generated over three stages of tectonic activity. By comparing surface observations to expected evidence of different sources of stress, such as uplift from local volcanoes or dyke intrusion, we found that each stage of tectonic activity had a different origin. A combination of local (from within Tempe Terra) and regional (from Tharsis) magmatic sources drove deformation, and tectonic activity began before the main structures and volcanoes of Tharsis had developed. Only two fault trends in Tempe Terra can be linked to regional stresses related to the growth of Tharsis: NNE-trending and ENE-trending faults. Isolating these regional trends provides clearer criteria for assessing models of Tharsis development in the future

Critical behavior of the two-dimensional N-component Landau-Ginzburg Hamiltonian with cubic anisotropy

We study the two-dimensional N-component Landau-Ginzburg Hamiltonian with cubic anisotropy. We compute and analyze the fixed-dimension perturbative expansion of the renormalization-group functions to four loops. The relations of these models with N-color Ashkin-Teller models, discrete cubic models, planar model with fourth order anisotropy, and structural phase transition in adsorbed monolayers are discussed. Our results for N=2 (XY model with cubic anisotropy) are compatible with the existence of a line of fixed points joining the Ising and the O(2) fixed points. Along this line the exponent $\eta$ has the constant value 1/4, while the exponent $\nu$ runs in a continuous and monotonic way from 1 to $\infty$ (from Ising to O(2)). For N\geq 3 we find a cubic fixed point in the region $u, v \geq 0$, which is marginally stable or unstable according to the sign of the perturbation. For the physical relevant case of N=3 we find the exponents $\eta=0.17(8)$ and $\nu=1.3(3)$ at the cubic transition.Comment: 14 pages, 9 figure

Organic chemistry. History and mutual relations of universities of Russia

The review describes the history of development of organic chemistry in higher schools of Russia over a period of 170 years, since the emergence of organic chemistry in our country till now. © 2017, Pleiades Publishing, Ltd

Organic chemistry. History and mutual relations of universities of Russia

The review describes the history of development of organic chemistry in higher schools of Russia over a period of 170 years, since the emergence of organic chemistry in our country till now. © 2017, Pleiades Publishing, Ltd