An intermittent detachment faulting system with a large sulfide deposit revealed by multi-scale magnetic surveys

AbstractMagmatic and tectonic processes can contribute to discontinuous crustal accretion and play an important role in hydrothermal circulation at ultraslow-spreading ridges, however, it is difficult to accurately describe the processes without an age framework to constrain crustal evolution. Here we report on a multi-scale magnetic survey that provides constraints on the fine-scale evolution of a detachment faulting system that hosts hydrothermal activity at 49.7°E on the Southwest Indian Ridge. Reconstruction of the multi-stage detachment faulting history shows a previous episode of detachment faulting took place 0.76~1.48 My BP, while the present fault has been active for the past ~0.33 My and is just in the prime of life. This fault sustains hydrothermal circulation that has the potential for developing a large sulfide deposit. High resolution multiscale magnetics allows us to constrain the relative balance between periods of detachment faulting and magmatism to better describe accretionary processes on an ultraslow spreading ridge.

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An intermittent detachment faulting system with a large sulfide deposit revealed by multi-scale magnetic surveys

10.21203/rs.3.rs-127728/v1 ◽

2020 ◽

Author(s):

Tao Wu ◽

Maurice Tivey ◽

Chunhui Tao ◽

Jinhui Zhang ◽

Fei Zhou ◽

...

Keyword(s):

Hydrothermal Activity ◽

Southwest Indian Ridge ◽

Sulfide Deposit ◽

Magnetic Survey ◽

Spreading Ridge ◽

Hydrothermal Circulation ◽

Crustal Accretion ◽

Multi Scale ◽

Multi Stage ◽

Detachment Faulting

Abstract Magmatic and tectonic processes can contribute to discontinuous crustal accretion and play an important role in hydrothermal circulation at ultraslow-spreading ridges, however, it is difficult to accurately describe the processes without an age framework to constrain crustal evolution. Here we report on a multi-scale magnetic survey that provides constraints on the fine-scale evolution of a detachment faulting system that hosts hydrothermal activity at 49.7°E on the Southwest Indian Ridge. Reconstruction of the multi-stage detachment faulting history shows a previous episode of detachment faulting took place 0.76~1.48 My BP, while the present fault has been active for the past ~0.33 My just in the prime of life. This fault sustains hydrothermal circulation that has the potential for developing a large sulfide deposit. High resolution multiscale magnetics allows us to constrain the relative balance between periods of detachment faulting and magmatism to better describe accretionary processes on an ultraslow spreading ridge.

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Application of Knowledge-Driven Methods for Mineral Prospectivity Mapping of Polymetallic Sulfide Deposits in the Southwest Indian Ridge between 46° and 52°E

Minerals ◽

10.3390/min10110970 ◽

2020 ◽

Vol 10 (11) ◽

pp. 970

Author(s):

Yao Ma ◽

Jiangnan Zhao ◽

Yu Sui ◽

Shili Liao ◽

Zongyao Zhang

Keyword(s):

Fuzzy Logic ◽

Fuzzy Ahp ◽

Hydrothermal Activity ◽

Southwest Indian Ridge ◽

Sulfide Deposit ◽

Southwest Indian Ocean ◽

Sulfide Deposits ◽

Mineral Prospectivity Mapping ◽

Mineral Prospectivity ◽

Prospectivity Mapping

As a product of hydrothermal activity, seafloor polymetallic sulfide deposit has become the focus of marine mineral exploration due to its great prospects for mineralization potential. The mineral prospectivity mapping is a multiple process that involves weighting and integrating evidential layers to further explore the potential target areas, which can be categorized into data-driven and knowledge-driven methods. This paper describes the application of fuzzy logic and fuzzy analytic hierarchy process (AHP) models to process the data of the Southwest Indian Ocean Mid-Ridge seafloor sulfide deposit and delineate prospect areas. Nine spatial evidential layers representing the controlling factors for the formation and occurrence of polymetallic sulfide deposit were extracted to establish a prospecting prediction model. Fuzzy logic and fuzzy AHP models combine expert experience and fuzzy sets to assign weights to each layer and integrate the evidence layers to generate prospectivity map. Based on prediction-area (P-A) model, the optimal gamma operator (γ) values were determined to be 0.95 and 0.90 for fuzzy logic and fuzzy AHP to synthesize the evidence layers. The concentration-area (C-A) fractal method was used to classify different levels of metallogenic probability by determining corresponding thresholds. Finally, Receiver Operating Characteristic (ROC) curves were applied to measure the performance of the two prospectivity models. The results show that the areas under the ROC curve of the fuzzy logic and the fuzzy AHP model are 0.813 and 0.887, respectively, indicating that prediction based on knowledge-driven methods can effectively predict the metallogenic favorable area in the study area, opening the door for future exploration of seafloor polymetallic sulfide deposits.

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