scholarly journals Building Objective 3D Fault Representations in Active Tectonic Settings

2017 ◽  
Vol 88 (3) ◽  
pp. 831-839 ◽  
Author(s):  
Magali Riesner ◽  
Pauline Durand‐Riard ◽  
Judith Hubbard ◽  
Andreas Plesch ◽  
John H. Shaw
Keyword(s):  
Active Tectonic ◽  
Tectonic Settings

scholarly journals Structural disorder of graphite and implications for graphite thermometry

Solid Earth ◽  
2018 ◽  
Vol 9 (1) ◽  
pp. 223-231 ◽  
Author(s):  
Martina Kirilova ◽  
Virginia Toy ◽  
Jeremy S. Rooney ◽  
Carolina Giorgetti ◽  
Keith C. Gordon ◽  
...  
Keyword(s):  
Irreversible Process ◽  
Carbonaceous Material ◽  
Graphite Powder ◽  
Structural Disorder ◽  
Structural Order ◽  
Active Tectonic ◽  
Graphite Structure ◽  
Tectonic Settings ◽  
Host Rocks ◽  
Crystalline Graphite

Abstract. Graphitization, or the progressive maturation of carbonaceous material, is considered an irreversible process. Thus, the degree of graphite crystallinity, or its structural order, has been calibrated as an indicator of the peak metamorphic temperatures experienced by the host rocks. However, discrepancies between temperatures indicated by graphite crystallinity versus other thermometers have been documented in deformed rocks. To examine the possibility of mechanical modifications of graphite structure and the potential impacts on graphite thermometry, we performed laboratory deformation experiments. We sheared highly crystalline graphite powder at normal stresses of 5 and 25  megapascal (MPa) and aseismic velocities of 1, 10 and 100 µm s−1. The degree of structural order both in the starting and resulting materials was analyzed by Raman microspectroscopy. Our results demonstrate structural disorder of graphite, manifested as changes in the Raman spectra. Microstructural observations show that brittle processes caused the documented mechanical modifications of the aggregate graphite crystallinity. We conclude that the calibrated graphite thermometer is ambiguous in active tectonic settings.

How submarine channels (re)shape continental margins

2020 ◽  
Vol 90 (11) ◽  
pp. 1581-1600
Author(s):  
Luke A. Pettinga ◽  
Zane R. Jobe
Keyword(s):  
Continental Margin ◽  
Evolution Model ◽  
Sediment Supply ◽  
Tectonic Deformation ◽  
Continental Margins ◽  
Sedimentary Processes ◽  
Submarine Channels ◽  
Active Tectonic ◽  
Tectonic Settings ◽  
Longitudinal Profiles

ABSTRACT Submarine landscapes, like their terrestrial counterparts, are sculpted by autogenic sedimentary processes toward morphologies at equilibrium with their allogenic controls. While submarine channels and nearby, inter-channel continental-margin areas share boundary conditions (e.g., terrestrial sediment supply, tectonic deformation), there are significant differences between the style, recurrence, and magnitude of their respective autogenic sedimentary processes. We predict that these process-based differences affect the rates of geomorphic change and equilibrium (i.e., graded) morphologies of submarine-channel and continental-margin longitudinal profiles. To gain insight into this proposed relationship, we document, classify (using machine learning), and analyze longitudinal profiles from 50 siliciclastic continental margins and associated submarine channels which represent a range of sediment-supply regimes and tectonic settings. These profiles tend to evolve toward smooth, lower-gradient longitudinal profiles, and we created a “smoothness” metric as a proxy for the relative maturity of these profiles toward the idealized equilibrium profile. Generally, higher smoothness values occur in systems with larger sediment supply, and the smoothness of channels typically exceeds that of the associated continental margin. We propose that the high rates of erosion, bypass, and deposition via sediment gravity flows act to smooth and mature channel profiles more rapidly than the surrounding continental margin, which is dominated by less-energetic diffusive sedimentary processes. Additionally, tectonic deformation will act to reduce the smoothness of these longitudinal profiles. Importantly, the relationship between total sediment supply and the difference between smoothness values of associated continental margins and submarine channels (the “smoothness Δ”) follows separate trends in passive and active tectonic settings, which we attribute to the variability in relative rates of smoothness development between channelized and inter-channel environments in the presence or absence of tectonic deformation. We propose two endmember pathways by which continental margins and submarine channels coevolve towards their respective equilibrium profiles with increased sediment supply: 1) Coupled Evolution Model (common in passive tectonic settings), in which the smoothness Δ increases only slightly before remaining static, and 2) Decoupled Evolution Model (common in active tectonic settings), in which the smoothness Δ increases more rapidly and to a greater final value. Our analysis indicates that the interaction of the allogenic factors of sediment supply and tectonic deformation with the autogenic sedimentary processes characteristic of channelized and inter-channel areas of the continental margin may account for much of the variability between coevolution pathways and depositional architectures.

scholarly journals Structural Disorder of Graphite and Implications for Graphite Thermometry

2017 ◽  
Author(s):  
Martina Kirilova ◽  
Virginia Toy ◽  
Jeremy S. Rooney ◽  
Carolina Giorgetti ◽  
Keith C. Gordon ◽  
...  
Keyword(s):  
Shear Strain ◽  
Irreversible Process ◽  
Carbonaceous Material ◽  
Graphite Powder ◽  
Structural Disorder ◽  
Active Tectonic ◽  
Graphite Structure ◽  
Tectonic Settings ◽  
Host Rocks ◽  
Crystalline Graphite

Abstract. Graphitization, or the progressive maturation of carbonaceous material, is considered an irreversible process. Thus, the degree of graphite crystallinity has been calibrated as an indicator of the peak metamorphic temperatures experienced by the host rocks. However, discrepancies between temperatures indicated by graphite crystallinity versus other thermometers have been documented in deformed rocks. To examine the possibility of mechanical modifications of graphite structure and the potential impacts on graphite thermometry we performed laboratory deformation experiments. We sheared highly crystalline graphite powder at normal stresses of 5 and 25 MPa and aseismic slow sliding velocities of 1 µm/s, 10 µm/s and 100 µm/s. The degree of graphite crystallinity both in the starting and resulting materials was analyzed by Raman microspectroscopy. Our results demonstrate consistent decrease of graphite crystallinity with increasing shear strain. We conclude that the calibrated graphite thermometer is ambiguous in active tectonic settings and we suggest that a calibration that accounts for shear strain is needed.

Thermochronology in active tectonic settings

2009 ◽  
pp. 192-206
Author(s):  
Jean Braun ◽  
Peter van der Beek ◽  
Geoffrey Batt
Keyword(s):  
Active Tectonic ◽  
Tectonic Settings

Elliptical calderas in active tectonic settings: an experimental approach

2005 ◽  
Vol 144 (1-4) ◽  
pp. 119-136 ◽  
Author(s):  
E.P. Holohan ◽  
V.R. Troll ◽  
T.R. Walter ◽  
S. Münn ◽  
S. McDonnell ◽  
...  
Keyword(s):  
Experimental Approach ◽  
Active Tectonic ◽  
Tectonic Settings

TECTONIC SETTINGS AND METALLOGENISM OF THE EASTERN SEGMENT OF THE QIN-HANG BELT, SOUTH CHINA

2013 ◽  
Vol 32 (5) ◽  
pp. 57-66 ◽  
Author(s):  
Lei XU ◽  
Sanzhong LI ◽  
Xin LIU ◽  
Yanhui SUO ◽  
Qi WU ◽  
...  
Keyword(s):  
South China ◽  
Eastern Segment ◽  
Tectonic Settings
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