Abstract Based on field investigation，petrographic observation，and related geochemical analysis，the characteristics and genesis of the hypergene dissolved algal framework dolostone in the Upper Cambrian in Keping area，Tarim Basin，were studied.In macro-scale，hummocky and lenticular algal reef dolostone sandwiched between the tidal-flat dolostones. A large number of supergene dissolution pores developed due to the differential dissolution.In micro-scale，the rocks are mainly composed of dark mud-silt-sized dolomite enriched in algae and light-colored sparry dolomite cement.Mud-silt-sized dolomite has subhedral-anhedral shaped mosaic structure，and display dark-orange red luminescence.They have high concentration of Na and K，but lower concentration of Fe.The δ13C ranges between -0.572‰ and 0.124‰，with an average value of-0.116‰;the value of δ18O ranges between -5.391‰ and -4.983‰，with an average of-5.240‰.These characteristics indicate that the mud-silt-sized dolomite was formed in contemporaneously stage under relatively oxidizing and higher salinity conditions.The sparry dolomite cements filling between algal framework，are anhedral-subhedral shaped and medium-coarse crystalline sized.They show dark cathodoluminescence or non-luminous.The contents of Na and K are low，whereas the content of Fe is high.δ13C values range between -0.662‰ and -0.251‰，with an average value of-0.460‰;δ18O values range between -6.639‰ and -5.939‰，with an average value of-6.267‰.These data indicate that the sparry dolomite cement formed in a relative reduction environment during burial stage.Both mud-silt-sized dolomite and sparry dolomite cements share similar REE patterns with finely crystalline limestone: LREE are enriched，HREE are depleted，and there are Eu negative anomalies.It suggests that both of them derived from seawater dolomitization fluid.In dissolution aspect，sparry dolomite cements are more easily dissolved than mud-silt-sized algal framework dolomite.In the supergene dissolution process，the major elements，Ca and Mg of the sparry dolomite cements，decreased significantly，and the Mg/Ca value declines from 0.955 to 0.007. Trace elements of Na and K were lost obviously.The Na/Ca value declines from 3.8×10-4 reduced to 1.9×10-4，K/Ca value declines from 1.1×10-3 to below the detection limit.Distribution pattern of rare earth elements were not changed.These features suggest that hypergene dissolution process is dedolomitization with salinity decreases，and there were nearly no gains and losses of rare earth elements.
About author: He Kai，born in 1986，is a master degree candidate.Now he is mainly engaged in researches of sedimentology and carbonate reservoir geology.E-mail: hekai1518@163.com. About the correspoinding author Zhu Jingquan, born in 1956, is a research professor in Institute of Geology and Geophysics, Chinese Academy of Sciences. Now He is mainly engaged in sedimentology, reservoir sedimentology and sedimentary geology. E-mail:Jqzhu@mail.igcas.ac.cn.
Cite this article:
He Kai,Zhu Jingquan,You Xuelian et al. Geochemistry characteristics and their implications of hypergenedissolved algal framework dolostone in the Upper Cambrianin Keping area，Tarim Basin[J]. JOURNAL OF PALAEOGEOGRAPHY, 2013, 15(1): 77-94.
He Kai,Zhu Jingquan,You Xuelian et al. Geochemistry characteristics and their implications of hypergenedissolved algal framework dolostone in the Upper Cambrianin Keping area，Tarim Basin[J]. JOPC, 2013, 15(1): 77-94.
高志前，樊太亮，李岩，等.2006.塔里木盆地寒武—奥陶纪海平面升降变化规律研究［J］. 吉林大学学报(地球科学版)，549-556. 郭建华，沈昭国，李建明.1994.塔北东段下奥陶统白云石化作用［J］.石油与天然气地质，15(1):51-59. 韩银学，李忠，韩登林，等.2009.塔里木盆地塔北东部下奥陶统基质白云岩的稀土元素特征及其成因［J］.岩石学报，25(10):2405-2416. 何莹，鲍志东，沈安江，等.2006.塔里木盆地牙哈—英买力地区寒武系—下奥陶统白云岩形成机理［J］.沉积学报，24(6):806-818. 胡文瑄，陈琪，王小林，等.2010.白云岩储集层形成演化过程中不同流体作用的稀土元素判别模式［J］.石油与天然气地质，31(6):810-818. 胡忠贵，郑荣才，胡九珍，等.2009.川东—渝北地区黄龙组白云岩储集层稀土元素地球化学特征［J］.地质学报，83(6):782-790. 黄思静.2010.碳酸盐岩的成岩作用［M］.北京: 地质出版社，1-288. 黄思静，龚业超，黄可可，等.2010.埋藏历史对碳酸盐溶解—沉淀的影响：以四川盆地东北部三叠系飞仙关组和塔里木盆地北部奥陶系为例［J］.地球科学进展，25(40):381-390. 黄思静，胡作维，王春梅，等.2007.四川盆地东北部三叠系飞仙关组碳酸盐岩成岩作用和白云岩成因的研究现状和存在问题［J］.地球科学进展，22(5):495-503. 贾承造.1999.塔里木盆地构造特征与油气聚集规律［J］.新疆石油地质，20(3): 177-183. 金之钧，王清晨.2004.中国典型叠合盆地与油气成藏研究新进展：以塔里木盆地为例［J］.中国科学(D辑)，34(增1): 1-12. 康玉柱.2008.中国古生代碳酸盐岩古岩溶储集特征与油气分布［J］.天然气工业，28(6):1-12. 康玉柱，康志宏.1994.塔里木盆地构造演化与油气［J］.地球学报，(3-4): 180-191. 汤良杰，张一伟，金之钧，等.2004.塔里木盆地、柴达木盆地的开合旋回［J］.地质通报，23(3):254-260. 王小林，金之钧，胡文瑄，等.2009.塔里木盆地下古生界白云石微区REE配分特征及其成因研究［J］.中国科学(D辑)，39(6):721-733. 王旭，沈建伟，陈代钊，等.2011.塔里木盆地柯坪—巴楚地区早古生代白云岩类型及微量元素地球化学特征［J］.矿物岩石，31(2):23-32. 吴仕强，朱井泉，胡文瑄，等.2009.塔里木盆地寒武—奥陶系白云岩结构类型及其形成机理［J］.现代地质，23（4）：638-647. 吴仕强，朱井泉，王国学，等.2008.塔里木盆地寒武—奥陶系白云岩结构构造类型及其形成机理［J］.岩石学报，24(6):1390-1400. 谢小敏，胡文瑄，王小林，等.2009.新疆柯坪地区寒武纪—奥陶纪碳酸盐岩沉积旋回的碳氧同位素研究［J］.地球化学，38(1):75-88. 杨杰东，王宗哲.1994.新疆柯坪地区早古生代地层的碳、氧和锶同位素［J］.地质论评，40(4):377-385. 朱井泉，吴仕强，王国学，等.2008.塔里木盆地寒武—奥陶系主要白云岩类型及孔隙发育特征［J］.地学前缘，15(2):67-79. Allen P，Keith M L.1965.Carbon isotope ratios and palaeosalininities of purbeck-Wealden carbonates［J］.Nature，208(5017):1278-1289. Baker P A，Burns S J.1985.Occurrence and formation of dolomite in organic-rich continental-margin sediments［J］. AAPG Bulletin，69(11):1917-1930. Banner J L，Hanson G N.1990.Calculation of simultaneous isotopic and trace element variations during water-rock interaction with applications to carbonate diagenesis［J］.Geochimica et Cosmochimica Acta，54: 3123-3138. Bau M.1991.Rare element mobility during hydrothermal and metamorphic fluid rock interaction and the significance of the oxidation state of europium［J］.Chemical Geology，93(3-4): 219-230. Brand U，Veizer J.1980.Chemical diagenesis of multicomponent carbonate system-1: Trace elements［J］.Journal of Sed Petrology，50: 1219-1236. Durocher S，Aasm I S.1997.Dolomitization and neormorphism of Mississippian(Visean)Upper Debolt formation，Blueberry Field，northeastern British Columbia: Geologic，Petrologic，and chemical evidence［J］.AAPG Bulletin，81(6):954-977. Folk R L，Land L S.1975.Mg/Ca ratio and salinity: Two controls over crystallization of dolomite［J］.AAPG Bulletin，59(1):60-68. Frimmel H E.2009.Trace element distribution in Neoproterozoic carbonates as palaeoenvironmental indicator［J］.Chemical Geology，258(3-4): 338-353. Garrels R M，Christ C L.1965.Minerals，Solutions，and Equilibria［M］.San Francieco：Freeman，Cooper and Co.，450. Gao G Q，Land L S.1991.Early Ordovician Cool Creek Dolomite，Middle Arbuckle Group，Slick Hills，Sw Oklahoma，U.S.A.: Origin and Modification［J］.Journal of Sedimentary Research，61(2):161-173. James R H，Elderfield H.1996.Chemistry of ore-forming fluids and mineral formation rates in an active hydrothermal sulfide deposit on the Mid-Atlantic Ridge［J］.Geology，24(12):1147-1150. Kirmaci M Z，Akda K.2005.Origin of dolomite in the Late Cretaceous-Paleocene limestone turbidites，Eastern Pontides，Turkey［J］.Sedimentary Geology，181(1-2): 39-57. Land L S.1985.The origin of massive dolomite［J］.Journal of Geological Education，33:112-125. Land L S.1991.Dolomitization of the Hope Gate Formation(north Jamaica)by seawater: Reassessment of mixing zone dolomite［J］.In: Taylor H P，O′ Neil J R，Kaplan I R（eds）.Isotopic Signatures and Sedimentary Records.Lecture Notes in Earth Sciences.Berlin: Springer-Verlag，43: 49-68. Machel H G，Mountjoy E W.1986.Chemistry and environment of dolomitizarion-a reappraisal［J］.Earth-Science Reviews，23(3):175-222. Mattes B W，Mountjoy E W.1980.Burial dolomitization of the Upper Devonian Miette Buildup，Jasper National Park，Alberta［J］.In: Zenger D H，Dunham J B，Ethington R L(eds).Concepts and Models of Dolomitization.SEPM Special Publication，28: 259-297. Mazumdar A，Tanaka K， et al.2003.Characteristics of rare earth element abundances in shallow marine continental platform carbonates of Late Neoproterozoic successions from India［J］.Geochemical Journal，37(2):277-289. Mills R A，Elderfield H.1995.Rare earth element geochemistry of hydrothermal deposits from the active TAG Mound，26°N Mid-Atlantic Ridge［J］.Geochimica et Cosmochimica Acta，59(17):3511-3524. Morrow D W.1982.Diagenesis: The chemistry of the dolomitization and dolomite precipication［J］.Geoscience Canada，9(1):5-13. Popp B N，Anderson T F，Sandberg P A.1986.Textural and isotopic variations among constituents in middle Devonian limestones，north America［J］.Journal of Sedimentary Petrology，56(5):715-727. Qing H，Mountjoy E W.1989.Multistage dolomitization in Rainbow Buildups，Middle Devonian Keg River Formation，Alberta，Canada［J］.Journal of Sedimentary Petrology，59(1):114-126. Qing H R，Bosence D W J，Rose E P F.2001.Dolomitization by penesaline sea water in Early Jurassic peritidal platform carbonates，Gibraltar，western Mediterranean［J］.Sedimentology，48(1):153-163. Searl A.1994.Diagenesisdestruction of reservoir of potential in shallow marine sandstones of the Broadford Beds（Lower Jurassic），North west Scotland-depositional versus burial and thermal history controls on porosity destruction［J］.Marine and Petroleum Geology，11(2):131-147. Sverjensky D A.1984.Europium redox equilibria in aqueous solution［J］.Earth and Planetary Science Letters，67(1):70-78. Vandeginste V，Swennen R，Reed， et al. 2009.Host rock dolomitization and secondary porosity development in the Upper Devonian Cairn Formation of the Fairholme carbonate complex(South-west Alberta，Canadian Rockies): Diagenesis and geochemical modeling［J］.Sedimentology，56(7):2044-2060. Veizer J.1983.Chemical diagenesis of carbonate: Theory and application of trace element technique［C］. In: Stable Isotopes in Sedimentary Geology.Soc.Econ.Paleontologists Mineralogists Short Course No.10，3-1-3-100. Veizer J，Hoefs J.1976.Nature of 18O-16O and13C-12C secular trends in sedimentary carbonate rocks［J］.Geochimica et Cosmochimica Acta，40(11):1387-1395. Warren J.2000.Dolomite: Occurrence，evolution and economically important associations［J］.Earth-Science Reviews，52(1-3): 1-81.
