Zeolitization of the Dacitic Tuff in the Miocene Janggi Basin, SE Korea

Jinju Kim; Jong Ok Jeong; Young-Jae Shinn; Young Kwan Sohn

doi:10.9719/EEG.2022.55.1.63

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Econ. Environ. Geol. 2022; 55(1): 63-76

Published online February 28, 2022

https://doi.org/10.9719/EEG.2022.55.1.63

Zeolitization of the Dacitic Tuff in the Miocene Janggi Basin, SE Korea

Jinju Kim¹, Jong Ok Jeong^2,*, Young-Jae Shinn³, Young Kwan Sohn¹

Author Info. +

¹Department of Geology and Research Institute of Natural Science, Gyeongsang National University, Jinju, 52828, Republic of Korea
²Center for Research Facilities, Gyeongsang National University, Jinju, 52828, Republic of Korea
³Division of Convergence on Marine Science, Korea Maritime and Ocean University, Busan, 49112, Republic of Korea

Correspondence to : ^*Corresponding author : jojeong@gnu.ac.kr

Received: November 24, 2021; Revised: February 25, 2022; Accepted: February 25, 2022

This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/3.0) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided original work is properly cited.

Abstract

Dacitic tuffs, 97 to 118 m thick, were recovered from the lower part of the subsurface Seongdongri Formation, Janggi Basin, which was drilled to assess the potential for underground storage of carbon dioxide. The tuffs are divided into four depositional units(Unit 1 to 4) based on internal structures and particle componentry. Unit 1 and Units 3/4 are ignimbrites that accumulated in subaerial and subaqueous settings, respectively, whereas Unit 2 is braided-stream deposits that accumulated during a volcanic quiescence, and no dacitic tuff is observed. A series of analysis shows that mordenite and clinoptilolite mainly fill the vesicles of glass shards, suggesting their formation by replacement and dissolution of volcanic glass and precipitation from interstitial water during burial and diagenesis. Glass-replaced clinoptilolite has higher Si/Al ratios and Na contents than the vesicle-filling clinoptilolite in Units 3. However, the composition of clinoptilolite becomes identical in Unit 4, irrespective of the occurrence and location. This suggests that the Si/Al ratio and pH in the interstitial water increased with time because of the replacement and leaching of volcanic glass, and that the composition of interstitial water was different between the eastern and western parts of the basin during the formation of the clinoptilolite in Units 1 and 3. It is also inferred that the formation of the two zeolite minerals was sequential according to the depositional units, i.e., the clinoptilolite formed after the growth of mordenite. To summarize, during a volcanic quiescence after the deposition of Unit 1, pH was higher in the western part of the basin because of eastward tilting of the basin floor, and the zeolite ceased to grow because of the closure of the pore space as a result of the growth of smectite. On the other hand, clinoptilolite could grow in the eastern part of the basin in an open system affected by groundwater, where braided stream was developed. Afterwards, Units 3 and 4 were submerged under water because of the basin subsidence, and the alkali content of the interstitial water increased gradually, eventually becoming identical in the eastern and western parts of the basin. This study thus shows that volcanic deposits of similar composition can have variable distribution of zeolite mineral depending on the drainage and depositional environment of basins.

Keywords tuff, mordenite, clinoptilolite, zeolitization

장기분지 데사이트질 응회암의 불석화작용

김진주¹ · 정종옥^2,* · 신영재³ · 손영관¹

¹경상국립대학교 지질과학과
²경상국립대학교 공동실험실습관
³한국해양대학교 해양과학융합학부

요 약

이산화탄소 지중저장 가능성 평가를 위해 시추한 결과, 장기분지 성동리층에 97~118m 두께의 데사이트질 응회암이 확인되었으며 내부구조와 입자조성에 따라 4개의 퇴적단위(퇴적단위 1~4)로 구분되었다. 퇴적단위 1은 육성환경, 퇴적단위 3, 4는 수중환경에서 쌓인 화쇄류암(ignimbrite)이며, 퇴적단위 2는 화산휴지기에 쌓인 망상하천 퇴적암으로 데사이트질 응회암이 관찰되지 않는다. 박편분석결과, 모데나이트, 클리놉틸로라이트는 주로 유리를 교대하거나 기공을 충전하며 매몰-속성과정 동안 화산유리의 교대작용 및 용해-침전작용으로 생성된 것으로 보인다. 클리놉틸로라이트는 퇴적단위 3에서 유리를 교대하는 경우가 기공을 충전한 경우보다 Si/Al비와 Na함량이 높으며 퇴적단위 4에서는 산출상태 및 지역에 상관없이 조성이 동일해 지는데, 이는 화산유리의 교대 및 용탈작용이 진행될수록 공극수의 Si/Al비와 pH가 증가했으며, 퇴적단위 3의 클리놉틸로라이트가 생성될 당시 동-서쪽의 공극수 조성이 달랐음을 지시한다. 또한, 모데나이트의 성장이 끝난 후 클리놉틸로라이트가 생성되었으며, 두 불석광물은 각 퇴적단위별로 순차적으로 생성된 것으로 해석된다. 종합해보면, 퇴적단위 1이 쌓인 후, 화산휴지기 동안 서고동저의 분지지형으로 인해 서쪽은 pH가 더 높았으나 스멕타이트의 성장으로 공극이 폐쇄되어 더 이상 불석광물 이 성장하지 못한 반면, 동쪽은 망상하천이 발달한 개방계 상태에서 지하수의 영향을 받아 클리놉틸로라이트가 성장할 수 있었던 것으로 보인다. 이후 분지의 침강으로 퇴적단위 3, 4는 수중환경으로 변화였고 공극수는 점점 알칼리함량이 증가하여 결국 동-서쪽의 공극수 조성이 동일해 진 것으로 해석되었다. 이와 같이 유사한 조성의 응회암에서도 분지의 수계와 퇴적환경에 따라 다양한 불석광물이 공간적으로 다르게 분포할 수 있음을 보여준다.

주요어 응회암, 모데나이트, 클리놉틸로라이트, 불석화작용

Article

Research Paper

Econ. Environ. Geol. 2022; 55(1): 63-76

Published online February 28, 2022 https://doi.org/10.9719/EEG.2022.55.1.63

Zeolitization of the Dacitic Tuff in the Miocene Janggi Basin, SE Korea

Jinju Kim¹, Jong Ok Jeong^2,*, Young-Jae Shinn³, Young Kwan Sohn¹

Correspondence to:^*Corresponding author : jojeong@gnu.ac.kr

Received: November 24, 2021; Revised: February 25, 2022; Accepted: February 25, 2022

Abstract

Keywords tuff, mordenite, clinoptilolite, zeolitization

장기분지 데사이트질 응회암의 불석화작용

김진주¹ · 정종옥^2,* · 신영재³ · 손영관¹

¹경상국립대학교 지질과학과
²경상국립대학교 공동실험실습관
³한국해양대학교 해양과학융합학부

Received: November 24, 2021; Revised: February 25, 2022; Accepted: February 25, 2022

요 약

주요어 응회암, 모데나이트, 클리놉틸로라이트, 불석화작용

Fig 1.

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Figure 1.Tectonics and geological maps around the study area. (a) Map showing the physiographic and geological information of the Tertiary terrestrial basins on the SE Korean peninsula (b) Map providing information of detailed geological setting and location of six boreholes (red dots) in the Janggi Basin (from Kim et al., 2015).

Economic and Environmental Geology 2022; 55: 63-76https://doi.org/10.9719/EEG.2022.55.1.63

Fig 2.

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Figure 2.(a) Stratigraphic correlation among the recovered 6 drill cores from the Janggi Basin (Gu et al., 2016) (b) Stratigraphic correlation of targeted volcaniclastic sequence within the Seongdongri Formation (Gim, 2016). Red rectangles in Fig. 2a indicate stratigraphic position of the target sequence in Fig. 2b.

Economic and Environmental Geology 2022; 55: 63-76https://doi.org/10.9719/EEG.2022.55.1.63

Fig 3.

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Figure 3.Slab photographs and thin-section photomicrographs of tuff units. (a) Core slab photograph of fine ash-rich massive lapilli tuff (aLTm) and (b) Thin-section photomicrograph (Unit 1, 666 m depth, JG1 well, Crossed nicol). Crystal and lithic fragments are supported by very fine to fine-grained ash. (c) Core slab photograph of fine ash-depleted massive lapilli tuff (adLTm, JG1 well) at 633m and its (d) Thin-section photomicrograph at 440m (Unit 3, JG3 well, Crossed nicol). (e) Core slab photograph of crystal-rich massive lapilli tuff at 604m (cLTm, JG1) and its (f) Thin-section photomicrograph at 402m (Unit 4, JG3 well, Crossed nicol).

Economic and Environmental Geology 2022; 55: 63-76https://doi.org/10.9719/EEG.2022.55.1.63

Fig 4.

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Figure 4.Back-scattered electron (BSE) images of zeolites in Unit 1. (a), (c) Western drilling sites (JG 1, JG 4). Pores are filled with Quartz, K-feldspar and Mordenite grown into radial fibers along the margin of the pore walls or glass shards. The remaining part in pores include fibrous smectite. (b), (d) Eastern drilling sites (JG3, JG5, JG6). Clinoptilolite fills the space occupied by smectite in the western drilling sites.

Economic and Environmental Geology 2022; 55: 63-76https://doi.org/10.9719/EEG.2022.55.1.63

Fig 5.

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Figure 5.Back-scattered electron (BSE) images of zeolites in Unit 3 and 4. (a), (b) Analcime observed in JG4 (unit 3, 690 m), grown along the boundaries between the matrix and crystals. (c), (d) Back-scattered electron (BSE) images of zeolites in JG3 (unit 4, 402m). Quartz, K-feldspar and smectite are grown along the margins of the pores. Mordenite grew in the pores whereas clinoptilolite grew in the pores or glass shards.

Economic and Environmental Geology 2022; 55: 63-76https://doi.org/10.9719/EEG.2022.55.1.63

Fig 6.

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Figure 6.X-ray diffraction patterns of dacitic tuffs in Unit 1. Top to bottom variation of diffraction pattern represents west to east variation of mineral assemblage in the Janggi Basin (JG: Janggi, U: Unit, aLTm: fine ash-rich massive lapilli tuff).

Economic and Environmental Geology 2022; 55: 63-76https://doi.org/10.9719/EEG.2022.55.1.63

Fig 7.

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Figure 7.X-ray diffraction patterns of dacitic tuffs in Unit 3. Top to bottom variation of diffraction pattern represents west to east variation of mineral assemblage in the Janggi Basin (JG: Janggi, U: Unit, wTm: well-sorted massive or crudely stratified tuff, adLTm: fine ash-depleted massive lapilli tuff, lLTm: Lithic-rich massive lapilli tuff).

Economic and Environmental Geology 2022; 55: 63-76https://doi.org/10.9719/EEG.2022.55.1.63

Fig 8.

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Figure 8.X-ray diffraction patterns of dacitic tuffs in Unit 4. Top to bottom variation of diffraction pattern represents west to east variation of mineral assemblage in the Janggi Basin (JG: Janggi, U: Unit, Lts: stratified lapilli tuff, cLTm: crystal-rich massive lapilli tuff).

Economic and Environmental Geology 2022; 55: 63-76https://doi.org/10.9719/EEG.2022.55.1.63

Fig 9.

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Figure 9.Vertical- lateral variations of mordenite and clinoptilolite abundance in tuff units. mordenite decreases or disappears above Unit 3 whereas clinoptilolite become abundant above Unit 3.

Economic and Environmental Geology 2022; 55: 63-76https://doi.org/10.9719/EEG.2022.55.1.63

Fig 10.

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Figure 10.(a) Alkali abundance ratios vs Si/Al ratios of mordenite. (b) Alkali abundance ratios vs Si/Al ratios of clinoptilolite. The Si/Al ratio of unit 1 is relatively low and increases gradually toward unit 4 (JG: Janggi, U: Unit).

Economic and Environmental Geology 2022; 55: 63-76https://doi.org/10.9719/EEG.2022.55.1.63

Fig 11.

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Figure 11.Triangular diagram for K, Ca and Na composition of mordenite of unit 1 and 4. In unit 1, the Na content is higher in the west, and the composition becomes the same in unit 4 (JG: Janggi, U: Unit).

Economic and Environmental Geology 2022; 55: 63-76https://doi.org/10.9719/EEG.2022.55.1.63

Fig 12.

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Figure 12.Ternary diagrams showing the compositional variation of cations in the Janggi clinoptilolite. In the west, K content is higher than in the east, and in both east and west, Na content is increased. In unit 1 and 3, the clinoptilolite filling the glass shard has a higher Na content than when it has grown into pore (JG: Janggi, U: Unit).

Economic and Environmental Geology 2022; 55: 63-76https://doi.org/10.9719/EEG.2022.55.1.63

Fig 13.

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Figure 13.(a) Illustration showing the environmental setting of the Janggi Basin during deposition of Unit 1. After unit 1 was deposited, the pH was higher in the west due to the influence of the meteoric water but the K, Na ion, flowed to the east. The pH continued to increase toward the east due to the influence of groundwater in the open system where the braided stream has developed. (b) Unit 3, 4. The sedimentary environment changed from subaerial to subaqueous environment due to the basin subsidence, and pH of pore water increased.

Economic and Environmental Geology 2022; 55: 63-76https://doi.org/10.9719/EEG.2022.55.1.63

Table 1 . Chemical composition and structural formulae of clinoptilolite(Si/Al ratios > 4) and heulandite(Si/Al ratios < 4) in volcanic glass from Janggi-core (JG: Janggi, U: Unit).

Volcanic glass
	West				East
Core-unit	JG4U3-690m	JG4U3-690m	JG1U4-601m	JG1U4-601m	JG3U1-479m	JG3U1-479m	JG3U3-435m	JG3U3-435m	JG3U4-402m	JG3U4-402m
SiO₂	66.86	68.51	67.12	68.85	64.99	67.13	67.65	66.63	67.70	67.44
TiO₂	0.07	0.04	0.03	0.04	0.06	0.05	0.08	0.02	0.06	0.12
Al₂O₃	13.07	12.54	13.27	12.64	14.60	13.37	13.90	12.47	12.81	12.71
Fe₂O₃	0.07	0.05	0.27	0.29	0.05	0.07	0.00	0.00	0.18	0.09
MnO	0.01	0.00	0.00	0.02	0.00	0.00	0.00	0.01	0.01	0.02
MgO	0.07	0.05	0.09	0.06	0.04	0.01	0.06	0.00	0.04	0.00
BaO	0.59	0.06	0.32	0.19	0.48	0.28	0.15	0.15	0.41	0.32
SrO	0.00	0.10	0.14	0.10	0.39	0.00	0.00	0.00	0.10	0.05
CaO	3.53	3.55	3.37	3.15	4.70	4.05	3.72	3.64	3.49	3.49
Na₂O	2.88	3.20	2.65	3.28	2.06	2.98	2.50	3.09	3.26	2.31
K₂O	1.09	1.04	1.09	1.02	0.47	0.47	0.49	0.38	0.80	1.37
Total	88.24	89.14	88.35	89.64	87.84	88.41	88.55	86.39	88.86	87.92
	Cation numbers on the basis of 77 oxygen charges
Si	29.25	29.54	29.24	29.53	28.58	29.17	29.20	29.51	29.36	29.48
Ti	0.04	0.02	0.01	0.02	0.03	0.03	0.04	0.01	0.03	0.06
Al	6.74	6.37	6.82	6.39	7.57	6.85	7.07	6.51	6.55	6.55
Fe3+	0.02	0.02	0.09	0.09	0.02	0.02	0.00	0.00	0.06	0.03
Mn	0.00	0.00	0.00	0.01	0.00	0.00	0.00	0.01	0.00	0.02
Mg	0.05	0.03	0.06	0.04	0.02	0.01	0.04	0.00	0.03	0.00
Ba	0.10	0.01	0.05	0.03	0.08	0.05	0.03	0.03	0.07	0.05
Sr	0.00	0.02	0.04	0.02	0.10	0.00	0.00	0.00	0.02	0.01
Ca	1.65	1.64	1.57	1.45	2.21	1.88	1.72	1.73	1.62	1.63
Na	2.44	2.67	2.24	2.73	1.76	2.51	2.09	2.65	2.74	1.95
K	0.61	0.57	0.60	0.56	0.27	0.26	0.27	0.22	0.44	0.76
Si/Al	4.34	4.64	4.29	4.62	3.78	4.26	4.13	4.53	4.48	4.50

Table 2 . Chemical composition and structural formulae of clinoptilolite(Si/Al ratios > 4) and heulandite(Si/Al ratios < 4) in pore from Janggi-core (JG: Janggi, U: Unit).

Pore
	West				East
Core-unit	JG4U3-690m	JG4U3-690m	JG1U4-601m	JG1U4-601m	JG3U1-479m	JG3U1-479m	JG3U3-435m	JG3U3-435m	JG3U4-402m	JG3U4-402m
SiO₂	69.69	69.17	69.74	70.43	61.93	63.92	66.24	68.76	66.27	68.50
TiO₂	0.00	0.01	0.04	0.03	0.03	0.08	0.01	0.02	0.00	0.04
Al₂O₃	12.92	14.38	12.94	13.00	17.09	15.40	14.44	13.20	13.74	13.56
Fe₂O₃	0.02	0.02	0.09	0.30	0.10	0.06	0.06	0.01	0.19	0.09
MnO	0.00	0.00	0.00	0.01	0.01	0.00	0.00	0.00	0.00	0.00
MgO	0.05	0.07	0.02	0.05	0.05	0.01	0.02	0.02	0.04	0.06
BaO	0.11	0.30	0.22	0.04	1.11	0.19	0.09	0.04	0.30	0.48
SrO	0.05	0.00	0.05	0.00	0.39	0.00	0.14	0.14	0.00	0.19
CaO	3.44	3.39	3.13	3.25	6.24	4.80	4.37	3.78	3.89	3.74
Na₂O	2.07	1.88	3.32	3.36	2.00	1.88	2.97	3.07	2.53	2.88
K₂O	1.43	1.18	0.67	0.80	0.38	0.38	0.47	0.56	1.06	0.75
Total	89.78	90.40	90.22	91.27	89.33	86.72	88.81	89.60	88.02	90.29
	Cation numbers on the basis of 77 oxygen charges
Si	29.69	29.26	29.60	29.56	27.22	28.38	28.71	29.40	29.00	29.22
Ti	0.00	0.01	0.02	0.01	0.01	0.04	0.00	0.01	0.00	0.02
Al	6.49	7.17	6.47	6.43	8.85	7.80	7.38	6.65	7.09	6.82
Fe3+	0.01	0.01	0.03	0.09	0.03	0.01	0.02	0.00	0.06	0.03
Mn	0.00	0.00	0.00	0.01	0.01	0.00	0.00	0.00	0.00	0.00
Mg	0.03	0.04	0.02	0.03	0.03	0.00	0.01	0.01	0.04	0.04
Ba	0.02	0.05	0.04	0.01	0.19	0.06	0.02	0.01	0.05	0.08
Sr	0.01	0.00	0.01	0.00	0.10	0.00	0.04	0.04	0.00	0.05
Ca	1.57	1.54	1.42	1.46	2.94	2.44	2.03	1.73	1.82	1.71
Na	1.71	1.54	2.73	2.73	1.71	1.62	2.49	2.55	2.14	2.38
K	0.78	0.64	0.37	0.43	0.21	0.25	0.26	0.31	0.59	0.41
Si/Al	4.58	4.08	4.57	4.60	3.07	3.64	3.89	4.42	4.09	4.28

Table 3 . Chemical composition and structural formulae of mordenite (in pore) from Janggi-core (JG: Janggi, U: Unit).

West					East
Core-unit	JG1U1-666m	JG1U1-666m	JG1U4-601m	JG1U4-601m	JG3U1-479m	JG3U1-479m
SiO₂	65.85	66.46	67.30	67.09	69.03	68.90
TiO₂	0.00	0.13	0.00	0.04	0.06	0.04
Al₂O₃	12.71	13.13	13.19	12.60	13.80	13.11
Fe₂O₃	0.00	0.05	0.06	0.08	0.05	0.00
MnO	0.01	0.00	0.01	0.02	0.01	0.00
MgO	0.01	0.02	0.00	0.02	0.00	0.00
BaO	0.00	0.26	0.02	0.04	0.00	0.00
SrO	0.00	0.29	0.00	0.10	0.00	0.00
CaO	2.75	2.65	2.68	2.89	3.36	3.36
Na₂O	4.17	3.04	4.27	4.05	3.57	3.41
K₂O	0.27	0.15	0.28	0.15	0.13	0.15
Total	85.78	86.19	87.80	87.09	90.01	88.98
Cation numbers on the basis of 96 oxygen charges
Si	39.18	39.24	39.11	39.31	39.04	39.36
Ti	0.00	0.06	0.00	0.02	0.02	0.02
Al	8.91	9.14	9.03	8.70	9.20	8.83
Fe3+	0.00	0.02	0.03	0.04	0.02	0.00
Mn	0.00	0.00	0.01	0.01	0.00	0.00
Mg	0.01	0.02	0.00	0.01	0.00	0.00
Ba	0.00	0.06	0.00	0.01	0.00	0.00
Sr	0.00	0.10	0.00	0.03	0.00	0.00
Ca	1.75	1.68	1.67	1.81	2.04	2.06
Na	4.81	3.48	4.81	4.60	3.91	3.78
K	0.21	0.12	0.21	0.11	0.09	0.11
Si/Al	4.40	4.29	4.33	4.52	4.24	4.46

Dec 31, 2024 Vol.57 No.6, pp. 665~835

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Research Paper

Zeolitization of the Dacitic Tuff in the Miocene Janggi Basin, SE Korea

Abstract

장기분지 데사이트질 응회암의 불석화작용

요 약

Article

Research Paper

Zeolitization of the Dacitic Tuff in the Miocene Janggi Basin, SE Korea

Abstract

장기분지 데사이트질 응회암의 불석화작용

요 약

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