• M R KAPAWAR

Articles written in Journal of Earth System Science

• Paleointensity of the Earth's magnetic field at ${\sim}$117 Ma determined from the Rajmahal and Sylhet Trap Basalts, India

We present here the paleointensity results of basalt samples from Rajmahal (25.10$^{\circ}$N; 87.40$^{\circ}$E) and Sylhet Traps (25.22$^{\circ}$N; 91.71$^{\circ}$E) of eastern India (${\sim}$117 Ma) to know the strength of the earth's magnetic field during the early Cretaceous from these locations. The modified version of the Thellier–Thellier paleointensity method of, in field-zero field-zero field-in field (IZZI) protocol and systematic partial thermoremanent magnetization (pTRM) checks were used for the paleointensity determination. Rock magnetic investigations on these rocks indicate ‘magnetite’ is the main remanence carrier with single domain (SD) to pseudosingle domain (PSD) nature. The samples have yielded low paleofield intensities between 6.97 $\pm$ 2.21 and 23.47 $\pm$ 2.08 $\mu$T (mean 17.20 $\pm$ 1.89 $\mu$T). The corresponding virtual dipole moment (VDM) ranges from 1.16 to 4.17 $\times$ 10$^{22}$ Am$^{2}$ (mean 2.93 $\times$ 10$^{22}$ Am$^{2}$) which is approximated as to 30% of the present-day field strength (8 $\times$ 10$^{22}$ Am$^{2}$). The success rate of the experiment is quite low in the order of 5%, but has provided scope for further, more elaborative paleointensity studies. Our new results compared with published paleointensities from these basalts as well as rocks of Cretaceous normal superchron (CNS) time around the globe are in good agreement.

• Mineral magnetic and geochemical characterization of the dust and soils around Mejia Thermal Power Plant, West Bengal: Implications to source apportionment

Characterization of magnetic, morphological, chemical properties and source apportionment of environmental transporters (dust and soil) around Mejia Thermal Power Station (MTPS), West Bengal, India were performed. Rock magnetic measurements combined with scanning electron microscopy (SEM) and X-ray fluorescence (XRF) study distinguish the mineral magnetic phases and identify their environmental implications concerning anthropogenic and natural factors. Findings of this study strengthen detection of anthropogenic magnetite, contributed by traffic and MTPS emission in dust and soil, respectively. However, presence of antiferromagnetic minerals in residential areas confirms their lithogenic and/or pedogenic origin. Existence of a low amount of anthropogenic magnetite in residential areas indicates their onset from fly ash emission due to prevailing north-easterly wind direction. Both soil and dust samples are categorized into three types of ferrimagnetic particles (spherules, irregular, and aggregate) with diverse morphologies and enriched iron concentration. Soil and dust were influenced by quartz, while the average concentrations of potentially toxic elements (PTEs) occurred in decreasing order of Ba${\ge}$Zr${\ge}$Cr${\ge}$V${\ge}$Sr${\ge}$Zn${\ge}$Y${\ge}$Nb${\ge}$Pb${\ge}$Co${\ge}$Sc${\ge}$Ga${\ge}$Ni. Sampling sites near ash pond with higher concentrations of PTEs than those situated at distance suggest that PTEs association with fly ash happened during coal combustion. This explains the observed correlation between magnetite particles and proxies for multiple pollution sources (like MTPS and traffic). It also reveals the necessity for attention when detecting abundance of anthropogenic magnetite using environmental magnetic methods. Thus, the identification of magnetite using environmental magnetic measurements can be used as a tracer for natural loading within anthropogenic background.

• # Journal of Earth System Science

Volume 131, 2022
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Continuous Article Publishing mode

• # Editorial Note on Continuous Article Publication

Posted on July 25, 2019