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<p>In this contribution, we present a comprehensive study of the aplitic dikes that exhibit cross-cutting relationships with the rhyolites and quartzites of the Mikir Massif in the Assam–Meghalaya Gneissic Complex (AMGC). These aplitic intrusions are thought to stem from granitic magmatism attributed to the Pan-African magmatic event in the AMGC. Petrographic, mineral chemical, and geochemical analyses allowed us to ascertain the nature and evolution of the aplites. The two-feldspar subsolvus nature of the granites and the distinct variations in elemental abundances (Ba, Rb, Sr, K/Rb, and Ba/Rb) unveil the genetic relationship between the granites and studied aplites. The observed high-silica dikes are characterised by two main textural units: (i) finer granophyric aplites and (ii) relatively coarser aplites with coarser granophyric texture. We also implemented fractal dimension (D<sub>B</sub>) and lacunarity (Λ) calculations to quantify and assess the two granophyric variants from the aplitic dikes and comment on the significant effect of undercooling resulting in textural heterogeneity. Such textural heterogeneity also implies variations in nucleation and growth rates influenced by migration of H<sub>2</sub>O from the margin of the dikes owing to rapid undercooling and build-up of H<sub>2</sub>O in the core, influencing crystallisation dynamics. Moreover, the intrusion of hot-aplitic magma into the host rhyolites facilitated significant release of heat and H<sub>2</sub>O, inducing low-degree partial melting of the host, which later injected back into the intrusive aplites as back-veining. This study addresses the processes governing the generation of aplitic magmas in the Mikir Massif and provides an intricate comprehension about their post-emplacement evolution.</p> Graphical Abstract <p></p>

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Tracing magma genesis and post-emplacement processes of aplites in the Mikir Massif, Northeast India: implementing fractal dimension and lacunarity analyses to decode textural heterogeneity

  • 期刊论文

  • 发表日期：

    2026年2月7日

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  • Pallabi Basumatary,
  • Tribujjal Prakash,
  • Hiredya Chauhan,
  • Bibhuti Gogoi

摘要

In this contribution, we present a comprehensive study of the aplitic dikes that exhibit cross-cutting relationships with the rhyolites and quartzites of the Mikir Massif in the Assam–Meghalaya Gneissic Complex (AMGC). These aplitic intrusions are thought to stem from granitic magmatism attributed to the Pan-African magmatic event in the AMGC. Petrographic, mineral chemical, and geochemical analyses allowed us to ascertain the nature and evolution of the aplites. The two-feldspar subsolvus nature of the granites and the distinct variations in elemental abundances (Ba, Rb, Sr, K/Rb, and Ba/Rb) unveil the genetic relationship between the granites and studied aplites. The observed high-silica dikes are characterised by two main textural units: (i) finer granophyric aplites and (ii) relatively coarser aplites with coarser granophyric texture. We also implemented fractal dimension (DB) and lacunarity (Λ) calculations to quantify and assess the two granophyric variants from the aplitic dikes and comment on the significant effect of undercooling resulting in textural heterogeneity. Such textural heterogeneity also implies variations in nucleation and growth rates influenced by migration of H2O from the margin of the dikes owing to rapid undercooling and build-up of H2O in the core, influencing crystallisation dynamics. Moreover, the intrusion of hot-aplitic magma into the host rhyolites facilitated significant release of heat and H2O, inducing low-degree partial melting of the host, which later injected back into the intrusive aplites as back-veining. This study addresses the processes governing the generation of aplitic magmas in the Mikir Massif and provides an intricate comprehension about their post-emplacement evolution.

Graphical Abstract