Tectonic Setting and Environment of Alkaline Lacustrine Source Rocks in the Lower Permian Fengcheng Formation of Mahu Sag

摘要/Abstract

摘要： Mahu sag is one of the most prolific oil-gas sags in the Junggar Basin. The high-quality lacustrine source rocks in the Lower Permian Fengcheng formation are considered as the oldest alkaline lacustrine deposits in China, which provides the resource foundation for the formation of hundred-mile oil province in northwestern margin of Junggar Basin. Based on the investigations of regional geology, sedimentology, mineralogy and petrology, Fengcheng formation is inferred to be developed in the post-orogenic extensional fault depression which is found on the Paleozoic basement in the western Junggar Basin. The formation is overall a set of fan delta-lacustrine deposits with the depocenter in the center of Mahu sag. Abundant alkaline minerals are observed in the Fengcheng formation, including reedmergnerite, northupite, shortite, searlesite, eitelite, wegscheiderite and nahcolite etc., which indicates a representative alkaline lacustrine facies with high salinity, distinct from other common saline-lacustrine deposits. The presence of shortite, wegscheiderite, reedmergnerite and searlesite confirms that the alkaline lacustrine source rocks of the Fengcheng formation were deposited in a closed and high-salinity lacustrine environment highly effected by deep hydrothermal fluids, not due to evaporation, which is also strongly associated with volcanic activities under the extensional fault depression setting.

关键词: Junggar Basin, Mahu sag, Fengcheng Formation, alkaline lacustrine source rock, extensional fault depression, hydrothermal process

Abstract: Mahu sag is one of the most prolific oil-gas sags in the Junggar Basin. The high-quality lacustrine source rocks in the Lower Permian Fengcheng formation are considered as the oldest alkaline lacustrine deposits in China, which provides the resource foundation for the formation of hundred-mile oil province in northwestern margin of Junggar Basin. Based on the investigations of regional geology, sedimentology, mineralogy and petrology, Fengcheng formation is inferred to be developed in the post-orogenic extensional fault depression which is found on the Paleozoic basement in the western Junggar Basin. The formation is overall a set of fan delta-lacustrine deposits with the depocenter in the center of Mahu sag. Abundant alkaline minerals are observed in the Fengcheng formation, including reedmergnerite, northupite, shortite, searlesite, eitelite, wegscheiderite and nahcolite etc., which indicates a representative alkaline lacustrine facies with high salinity, distinct from other common saline-lacustrine deposits. The presence of shortite, wegscheiderite, reedmergnerite and searlesite confirms that the alkaline lacustrine source rocks of the Fengcheng formation were deposited in a closed and high-salinity lacustrine environment highly effected by deep hydrothermal fluids, not due to evaporation, which is also strongly associated with volcanic activities under the extensional fault depression setting.

Key words: Junggar Basin, Mahu sag, Fengcheng Formation, alkaline lacustrine source rock, extensional fault depression, hydrothermal process

ZHANG Yuanyuan, LI Wei, TANG Wenbin. Tectonic Setting and Environment of Alkaline Lacustrine Source Rocks in the Lower Permian Fengcheng Formation of Mahu Sag[J]. 新疆石油地质, 2018, 39(zk(English) ): 151-156.

ZHANG Yuanyuan, LI Wei, TANG Wenbin. Tectonic Setting and Environment of Alkaline Lacustrine Source Rocks in the Lower Permian Fengcheng Formation of Mahu Sag[J]. Xinjiang Petroleum Geology, 2018, 39(zk(English) ): 151-156.

参考文献

[1] MA Zongjin,QU Guosheng,CHEN Xinfa.Tectonic framework and division in Junggar basin[J]. Xinjiang Petroleum Geology,2008,29(1):1-6.
[2] KUANG Lichun,TANG Yong,LEI Dewen,et al. Formation conditions and exploration potential of tight oil in the Permian saline lacustrine dolomitic rock,Junggar basin,NW China[J]. Petroleum Exploration and Development,2012,39(6): 657-667.
[3] CAO Jian,LEI Dewen,LI Yuwen,et al. Ancient high- quality alkaline lacustrine source rocks discovered in the Lower Permian Fengcheng formation,Junggar basin[J]. Acta Petrolei Sinica,2015,36(7): 781-790.
[4] ZHI Dongming,CAO Jian,XIANG Baoli,et al. Fengcheng alkaline lacustrine source rocks of Lower Permian in Mahu sag in Junggar basin:hydrocarbon generation mechanism and petroleum resources reestimation[J]. Xinjiang Petroleum Geology,2016,37(5):499-506.
[5] SMITH M E,CARROLL A R.Synoptic reconstruction of a major ancient lake system: Eocene Green River formation,western United States[J]. Geological Society of America Bulletin,2008,120(1-2): 54-84.
[6] GARCÍA-VEIGA S J,HELVACI B C. Mineralogy and sedimentology of the Miocene Göcenoluk borate deposit,Kırka district,western Anatolia,Turkey[J]. Sedimentary Geology,2013,290: 85-96.
[7] LI Minlu.The first discovery of Tertiary fractured dolomite reservoirs in Biyang depression[J]. Oil & Gas Geology,1984,5(4):402.
[8] QIU Longwei,JIANG Zaixing,CAO Yingchang,et al. Alkali diagenesis and their effect on the reservoirs in Biyang sag[J]. Science in China Series D: Earth Sciences,2001,31(9): 752-759.
[9] JAGNIECKI E A,LOWENSTEIN T K.Evaporites of the Green River formation,Bridger and Piceance Creek basins: deposition,diagenesis,paleobrine chemistry,and eocene atmospheric CO₂[M]//SMITH M E,CARROLL A R. Stratigraphy and paleolimnology of the Green River formation,Western USA. Springer,Netherlands,2015: 277-312.
[10] SHAO Yu,WANG Renfu,ZHANG Yueqian,et al. Strike-slip structures and oil-gas exploration in the NW margin of the Junggar basin,China[J]. Acta Petrolei Sinica,2011,32(6): 976-984.
[11] CHEN Shi,GUO Zhaojie,QI Jiafu,et al. Three stages of the strike-slip fault system in the West Junggar and the implications for the hydrocarbon exploration[J]. Oil ＆ Gas Geology,2016,37(3):322-331.
[12] QIN Zhijun,CHEN Lihua,LI Yuwen,et al. Paleosedimentary setting of the Lower Permian Fengcheng alkali lake in Mahu sag,Junggar basin[J]. Xinjiang Petroleum Geology,2016,37(1):1-6.
[13] CHEN Shi,GUO Zhaojie,PE-PIPER G,et al. Late Paleozoic peperites in West Junggar,China,and how they constrain regional tectonic and palaeoenvironmental setting[J]. Gondwana Research,2013,23(2): 666-681.
[14] CHEN Shi,PE-PIPER G,PIPERD J W,et al. Ophiolitic mélanges in crustal-scale fault zones: implications for the Late Palaeozoic tectonic evolution in West Junggar,China[J]. Tectonics,2014,33(12): 2 419-2 443.
[15] HAN Baofu,JI Jianqing,SONG Biao,et al. Late Paleozoic vertical growth of continental crust around the Junggar basin,Xinjiang,China(Part Ⅰ): timing of post-collisional plutonism[J]. Acta Petrologica Sinica,2006,22(5): 1 077-1 086.
[16] CHEN Shi,GUO Zhaojie.Time constraints,tectonic setting of Dalabuteophiolitic complex and its significance for Late Paleozoic tectonic evolution in West Junggar[J]. Acta Petrologica Sinica,2010,26(8): 2 336-2 344.
[17] LI Xinzi,HAN Baofu,JI Jianqing,et al. Geology,geochemistry and K-Ar ages of the Karamay basic-intermediate dyke swarm from Xinjiang,China[J]. Geochimica,2004,33(6): 574-584.
[18] ZHOU Jing, JI Jianqing, HAN Baofu, et al. ⁴⁰Ar/³⁹Ar geochronology of mafic dykes in north Xinjiang[J]. Acta Petrologica Sinica,2008,24(5): 997-1 010.
[19] ZHANG Yueqian,WANG Xin,LIU Jishan,et al. Wuerhe-Xiazijie strike-slip structure and petroleum exploration significance in northwestern margin of Junggar basin[J]. Xinjiang Petroleum Geology,2011,32(5):447-450.
[20] YI Zhiyu, HUANG Baochun, XIAO Wenjiao, et al. Paleomagnetic study of Late Paleozoic rocks in the Tacheng basin of West Junggar (NW China): implicationsfor the tectonic evolution of the western Altaids[J]. Gondwana Research,2015,27(2): 862-877.
[21] FENG Youliang,ZHANG Yijie,WANG Ruiju,et al. Dolomites genesis and hydrocarbon enrichment of the Fengcheng formation in the northwestern margin of Junggar basin[J]. Petroleum Exploration and Development,2011,38(6): 685-692.
[22] YU Kuanhong,CAO Yingchang,QIU Longwei,et al. Brine evolution of ancient lake and mechanism of carbonate minerals during the sedimentation of Early Permian Fengcheng formation in Mahu depression,Junggar basin,China[J]. Nature Gas Geoscience,2016,27(7):1 248-1 263.
[23] JIANG Yiqin,WEN Huaguo,QI Liqi,et al. Salt minerals and their genesis of the Permian Fengcheng formation in Urho area,Junggar basin[J]. Journal of Mineralogy and Petrology,2012,32(2): 105-114.
[24] CHANG Hailiang,ZHENG Rongcai,GUO Chunli,et al. Characteristics of rare earth elements of exhalative rock in Fengcheng formation,northwestern margin of Jungger basin[J]. Geological Review,2016,62(3):550-568.
[25] BRADLEY W H,EUGSTER H P.Geochemistry and paleolimnology of the trona deposits and associated authigenic minerals of the Green River formation of Wyoming[R]. USGS Professional Paper,1969:36-42.
[26] JAGNIECKI E A,JENKINS D M,LOWENSTEIN T K,et al. Experimental study of shortite (Na₂Ca₂(CO₃)₃) formation and application to the burial history of the Wilkins Peak Member,Green River basin,Wyoming,USA[J]. Geochimica et Cosmochimica Acta,2013,115(5): 31-45.
[27] WEGSCHEIDER R,MEHL J.ÜBER systeme Na₂CO₃-NaHCO₃-H₂O und das Existenzgebiet der Trona[J]. Monatshefte für Chemie und Verwandte Teile Anderer Wissenschaften,1928,49(1-2): 283-315.
WEGSCHEIDER R, MEHL J.System Na₂CO₃-NaHCO₃-H₂O and the presence of Trona[J]. Monatshefte für Chemie und verwandte Teile anderer Wissenschaften,1928,49(1-2): 283-315.
[28] BALL M C,STRACHANA N,STRACHANR M.Thermal decomposition of solid wegscheiderite,Na₂CO₃·3NaHCO₃[J]. Journal of the Chemical Society,Faraday Transactions,1991,87(12): 1 911-1 914.
[29] QU Yihua.Mineral and geological introduction of Kremer Boron deposit in California,USA[J]. Minerals and Rocks,1986,6(3):177-179.
[30] YANG Jianghai,YI Chenglong,DU Yuansheng,et al. Geochemical significance of the Paleogene soda-deposits bearing strata in Biyang depression,Henan province[J]. Science China: Earth Sciences,2014,44(10): 2172-2181
[31] WUNDER B,STEFANSKI J,WIRTH R,et al. Al-B substitution in the system albite (NaAlSi₃O₈)-reedmergnerite (NaBSi₃O₈)[J]. European Journal of Mineralogy,2013,25(4):499-508.
[32] SCHREYER W,WERDING G.High-pressure behaviour of selected boron minerals and the question of boron distribution between fluids and rocks[J]. Lithos,1997,41(1-3):251-266.
[33] ZHOU Zhongyi,PAN Changchun,FAN Shanfa,et al. Geothermal characteristics and its oil prospecting significance of the Junggar basin[J]. Xinjiang Petroleum Geology,1989,10(3):67-74.