Journal of earth system science | |
Roundness of survivor clasts as a discriminator for melting and crushing origin of fault rocks: A reappraisal | |
Arindam Sarkar^11  | |
[1] Department of Geology, University of Delhi, Delhi 110007, India.^1 | |
关键词: Pseudotachylyte; cataclasite; survivor clasts; roundness; melting; | |
DOI : | |
学科分类:天文学(综合) | |
来源: Indian Academy of Sciences | |
【 摘 要 】
Roundness of survivor clasts (mineral/rock fragments) in fault rocks (e.g., pseudotachylyte and cataclasite/gouge) has been used by some workers to distinguish melt-origin from crush-origin of such rocks. Keeping in view the large overlap in the published data on the roundness of fault rocks, the reliability of such a discriminator appears somewhat uncertain. The present study attempts to reappraise the aforesaid criterion through roundness analysis of quartz and feldspar clasts in melting-dominated pseudotachylyte (M-Pt), crushing-dominated pseudotachylyte (C-Pt) and fault-related cataclasite (F-Ct) collected from SarwarâJunia Fault Zone in Rajasthan and from GavilgarhâTan Shear Zone in central India. Our analysis shows that roundness of clasts cannot reliably distinguish between fault rocks of melt-origin and crush-origin (especially M-Pt and F-Ct) as the roundness values overlap and a distinct limit of roundness value for each rock type cannot be established. While the roundness of clasts in M-Pt and C-Pt may be enhanced due to melt-induced rounding off of the initially angular clasts, rounding of clasts can also occur by abrasion during rolling of crushed material in F-Ct. Furthermore, anomalous thermal expansion of clasts in melt-origin pseudotachylyte may cause disintegration of larger clasts into smaller angular fragments, thereby increasing the percentage of angular clasts in melt-origin fault rocks. Therefore, roundness of survivor clasts cannot be solely used as a discriminator between melt-origin and crush-origin fault rocks.
【 授权许可】
CC BY
【 预 览 】
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