Geology, Mineralization and Skarn Zonation of Tujulapan Block, an Updates from the Ruwai Polymetallic Skarn Deposit, Central Borneo, Indonesia: Implications to Exploration

Abstract:

The Ruwai polymetallic Fe–Zn–Pb–Ag skarn deposit, located in Lamandau Regency, Central Kalimantan is part of the Central Kalimantan metallogenic belt. Previous studies [Idrus et al., 2011; Setijadji et al., 2011; Cooke & Kitto, 1997; Simbolon et al., 2019; Dana et al., 2021] have outlined four main blocks—Gojo, Karim, Central Gossan, and Southwest Gossan—classified into proximal and distal skarn zones following Meinert’s [1997] zoning model. This study updates the metallogenic model by examining the newly identified Tujulapan Block, situated west of the Southwest Gossan Block, using data from ten drill holes supported by geological mapping and petrographic–mineragraphic analyses. The lithological assemblage in the Tujulapan Block—comprising volcanic rocks, metalimestone, siltstone, sandstone, hydrothermal breccia, and skarn deposits—closely resembles that of the Southwest Gossan Block. Prograde skarn minerals (pyroxene, garnet) and retrograde minerals (chlorite, epidote, calcite) are well developed, with ore mineralization occurring as massive, disseminated, and brecciated forms. Based on garnet–pyroxene ratios and elemental comparisons (Zn/Cu, Zn/Pb, Pb/Cu), the Tujulapan Block is interpreted as belonging to the distal skarn zone, despite containing notable magnetite mineralization. These findings refine the understanding of skarn zonation in the Ruwai system and provide strategic guidance for future exploration, highlighting both lateral and deeper mineralization potential within and beyond the Tujulapan Block.

• Periodical: Engineering Headway (Volume 39)
• Pages: 143-156
• DOI: https://doi.org/10.4028/p-ABzM9l
• Online since: July 2026
• Authors: Nico Andreas Nainggolan*, Adi Tonggiroh, Meutia Farida
• Keywords: Mineralization, Ruwai Polymetallic Skarn, Skarn Zonation

References

[1] Dana, C. D., Agangi, A., Idrus, A., Chelle-Michou, C., Lai, C. K., Ishida, M., & Xia, X. P. [2023]. The age and origin of the Ruwai polymetallic skarn deposit, Indonesia: evidence of Cretaceous Mineralization in the Central Borneo Metallogenic Belt. Economic Geology, 118[6], 1341-1370.

DOI: 10.5382/econgeo.5009

[2] Hall, R., Nichols, G., 2002. Cenozoic sedimentation and tectonics in Borneo: climatic influences on orogenesis. Geol. Soc. Spec. Publ. 191, 5–22. https://doi.org/10.1144/ GSL.SP.2002.191.01.02.

DOI: 10.1144/gsl.sp.2002.191.01.02

[3] Idrus, A., Setijadji, L.D., Tamba, F., Anggara, F., 2011. Geology and characteristics of Pb-Zn-Cu-Ag skarn deposit at Ruwai, Lamandau Regency, Central Kalimantan. J. Appl. Geol. 3, 191–201.

DOI: 10.22146/jag.7181

[4] Setijadji, L.D., Tamba, F., Idrus, A., 2011. Geology of the Ruwai iron and Zn-Pb-Ag skarn deposits Lamandau District, Central Kalimantan. Maj. Geol. Indones. 26, 143–154.

DOI: 10.22146/jag.7181

[5] Ayson, J.N.R., 1997. In: PT. Tebolai Seng Perdana – Summary of Exploration Activities [Preliminary Report]. PT. Tebolai Seng Perdana, p.1–56 unpublished internal report.

[6] Cooke, D., Kitto, P., 1997. In: Report on the Mineral Prospectivity of the Tebolai and Schwaner COW's, Southwest Kalimantan, Indonesia, p.1–49. Unpublished internal report.

[7] Simbolon, D., Dana, C.D.P., Whitehouse, L., 2019. Metallogenic model of the Ruwai Fe-Zn-Pb-Ag skarn deposit, Central Borneo: understanding the complexity from proximal to distal basemetal mineralization. In: Proceedings MGEI Unlocking Concealed and Complex Deposits [UCCD 2019], p.115–122. Bogor.

DOI: 10.3390/min12121564

[8] Dana, C.D.P., Agangi, A., Takahashi, R., Idrus, A., Lai, C.K., Nainggolan, N.A., 2022a. Element mobility during formation of the Ruwai Zn-Pb-Ag skarn deposit, Central Borneo, Indonesia. Resour. Geol. 72, e12290.

DOI: 10.1111/rge.12290

[9] Meinert, L.D., 1997. Application of skarn deposit zonation models to mineral exploration. Explor. Min. Geol. 6, 185–208.

[10] Chang, Z., & Meinert, L. D. [2008, November]. Zonation in skarns–complexities and controlling factors. In PACRIM Congress [pp.303-306].

[11] Margono, U., Soejitno, T. and Santosa, T. [1995] Geological Map of the Tumbangmanjul Quadrangle, Kalimantan. 1 sheet. Bandung: Geological Research and Development Centre of Indonesia,1:250000.

[12] Widyastanto, A., Brojomusti, J., Dana, C.D.P. and Fatratomo., Santayana, H. [2019] Mineralogical characteristics of granitoid and mafic intrusive bodies in Ruwai skarn Zn-Pb-Ag deposit: a preliminary study on pre to post mineralization intrusion. In: Proceeding of the Joint Convention Yogyakarta 2019, HAGI– IAGI– IAFMI- IATMI [JCY 2019]. Jakarta: Indonesian Association of Geologists, p.1–6.

[13] Idrus, A., Dana, C. D., Lai, C. K., Agangi, A., Takahashi, R., & Rajagukguk, E. H. [2023]. Proximal to distal geochemical variations of the Ruwai polymetallic skarn deposit, Central Borneo, Indonesia: Insights from sulfides chemistry and implications to exploration. Journal of Geochemical Exploration, 246, 107161.

DOI: 10.1016/j.gexplo.2023.107161

[14] Dana, C.D.P., Simarmata, J.R., Aditya, P.G.S. and Widyastanto, A. [2019] Hydrothermal alteration zoning and mineralization style in southwest gossan block of Ruwai skarn Zn-Pb-Ag deposit, Lamandau, Central Borneo: an implication to ore genesis and exploration. In: Proceeding of the Joint Convention Yogyakarta 2019, HAGI– IAGI– IAFMI- IATMI [JCY 2019]. Jakarta: Indonesian Association of Geologists, p.1–6.

DOI: 10.17014/ijog.v6i4.126

[15] Xu, R., Li, W. C., Deng, M. G., Zhou, J. X., Ren, T., & Yu, H. J. [2019]. Genesis of the superlarge Luziyuan Zn-Pb-Fe [-Cu] distal skarn deposit in western Yunnan [SW China]: Insights from ore geology and CHOS isotopes. Ore Geology Reviews, 107, 944-959.

DOI: 10.1016/j.oregeorev.2019.03.015

[16] Chang, Z., Shu, Q., & Meinert, L. D. [2019]. Skarn deposits of China.