The relationship between magnetic anisotropy, rock-strength anisotropy and vein emplacement in gold-bearing metabasalts of Gadag (South India)

Vishnu, C. S.; Lahiri, Sivaji; Mamtani, Manish A.

doi:10.1016/j.tecto.2017.09.011

Cited by 15 publications

(3 citation statements)

References 65 publications

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“…A favourably oriented anisotropy lowers the shear strength of the host rock, generating slip at a minimum compressive stress. Moreover, Vishnu et al (2018) have established a relationship between the magnetic anisotropy and rock strength anisotropy in the metabasalts of CSB. Thus, the pre-existing anisotropy of the metabasalts played a significant role in fracture propagation and vein emplacement .…”

Section: A States Of Stress and Fluid Pressure Conditionmentioning

confidence: 99%

Influence of fluid pressure changes on the reactivation potential of pre-existing fractures: a case study in the Archaean metavolcanics of the Chitradurga region, India

Bhowmick

Mondal

2021

Geol. Mag.

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The metavolcanics of Chitradurga region host numerous shallow crustal veins and fractures and faults of multiple orientations. Several high and low Pf cycles have been recorded in the region, leading to the reactivation of most of the pre-existing fractures for high Pf and selective reactivation of some well-oriented fractures under low Pf conditions. The pre-existing anisotropy (magnetic fabric) in the metavolcanics acted as the most prominent planar fabric for fracture propagation and vein emplacement under both conditions, thereby attaining maximum vein thickness. In this study, we emphasize the reactivation propensity of these pre-existing fracture planes under conditions of fluid pressure variation, related to the high and low Pf cycles. Multiple cycles of fluid-induced fracture reactivation make it difficult to quantify the maximum/minimum fluid pressure magnitudes. However, in this study we use the most appropriate fluid pressure magnitudes mathematically feasible for a shallow crustal depth of ∼2.4 km. We determine the changes in the reactivation potential with states of stress for the respective fracture orientations under both high and low Pf conditions. Dependence of fluid pressure variation on the opening angle of the fractures is also monitored. Finally, we comment on the failure mode and deformation behaviour of the fractures within the prevailing stress field inducing volumetric changes at the time of deformation. We find that deformation behaviour is directly related to the dip of the fracture planes.

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Section: A States Of Stress and Fluid Pressure Conditionmentioning

confidence: 99%

Influence of fluid pressure changes on the reactivation potential of pre-existing fractures: a case study in the Archaean metavolcanics of the Chitradurga region, India

Bhowmick

Mondal

2021

Geol. Mag.

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“…Moreover, we ask do the failure modes provide information on mechanical behaviour of virtually isotropic rocks such as metabasalts, within an external stress eld? The study of failure modes in rock mechanics provides an insight regarding the material strength, vis-àvis inherent fabric of the material (Szwedzicki 2007;Vishnu et al 2010Vishnu et al , 2018. The crystalline rocks preserve a range of micro-aws leading to the crack initiation, propagation and subsequent failure (Scholz 1968;Martin and Chandler 1994;Eberhardt et al 1998;Li et al 2003;Jaeger et al 2007).…”

Section: Introductionmentioning

confidence: 99%

An Experimental Approach to Evaluate the Role of Rock Failure Modes in Mechanical Characterization of Metabasalts

2022

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A detailed understanding on rock failure modes testi es the competence of support designs for engineering work. Studying such failure modes using physical models of rock samples under laboratory conditions can be time e cient, informative and economically viable. In this study, the mechanical behavior of massive metabasalts were characterized with reference to rock failure modes through index tests such as point load and Brazilian testing conditions. Rock failure modes under point load test are categorized as i) single plane failure mode, ii) triple junction failure mode, iii) twisted failure mode and iv) single plane (inclined). It is observed that twisted and triple junction failure modes are observed for the samples with higher point load strength values (> 6 MPa). A total of ve types of rock failure modes were observed in metabasalts under Brazilian testing conditions such as i) central multiple, ii) central, iii) noncentral, iv) central multiple + layer activation and v) conjugate failure modes. Central multiple failure mode is found to be the most common failure mode in metabasalts due to its massive nature. It is also observed that all failure modes under Brazilian test are transpired in the range of 8 to 12 MPa. Among all other perceived rock failure modes, single plane (inclined) and conjugate failure modes under point load and Brazilian tests respectively are introduced in this study. It is evident that rock failure modes, which lead to control the strength of the rocks, should be considered as an important aspect for mechanical characterization of rock materials.

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“…The study of failure modes in rock mechanics provides an insight regarding the material strength, vis-àvis inherent fabric of the material (Szwedzicki 2007;Vishnu et al 2010Vishnu et al , 2018. The crystalline rocks preserve a range of micro-aws leading to the crack initiation, propagation and subsequent failure (Scholz 1968;Martin and Chandler 1994;Eberhardt et al 1998;Li et al 2003;Jaeger et al 2007).…”

Section: Introductionmentioning

confidence: 99%

An experimental approach to evaluate the role of rock failure modes in mechanical characterization of metabasalts

Bhowmick¹,

Ram²,

Mondal³

2021

Preprint

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A detailed understanding on rock failure modes testifies the competence of support designs for engineering work. Studying such failure modes using physical models of rock samples under laboratory conditions can be time efficient, informative and economically viable. In this study, the mechanical behavior of massive metabasalts were characterized with reference to rock failure modes through index tests such as point load and Brazilian testing conditions. Rock failure modes under point load test are categorized as i) single plane failure mode, ii) triple junction failure mode, iii) twisted failure mode and iv) single plane (inclined). It is observed that twisted and triple junction failure modes are observed for the samples with higher point load strength values (> 6 MPa). A total of five types of rock failure modes were observed in metabasalts under Brazilian testing conditions such as i) central multiple, ii) central, iii) non-central, iv) central multiple + layer activation and v) conjugate failure modes. Central multiple failure mode is found to be the most common failure mode in metabasalts due to its massive nature. It is also observed that all failure modes under Brazilian test are transpired in the range of 8 to 12 MPa. Among all other perceived rock failure modes, single plane (inclined) and conjugate failure modes under point load and Brazilian tests respectively are introduced in this study. It is evident that rock failure modes, which lead to control the strength of the rocks, should be considered as an important aspect for mechanical characterization of rock materials.

show abstract

The relationship between magnetic anisotropy, rock-strength anisotropy and vein emplacement in gold-bearing metabasalts of Gadag (South India)

Cited by 15 publications

References 65 publications

Influence of fluid pressure changes on the reactivation potential of pre-existing fractures: a case study in the Archaean metavolcanics of the Chitradurga region, India

Influence of fluid pressure changes on the reactivation potential of pre-existing fractures: a case study in the Archaean metavolcanics of the Chitradurga region, India

An Experimental Approach to Evaluate the Role of Rock Failure Modes in Mechanical Characterization of Metabasalts

An experimental approach to evaluate the role of rock failure modes in mechanical characterization of metabasalts

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