摘要
鲁西地区保存有华北克拉通最典型的新太古代花岗-绿岩带,且后期地质作用改造较弱,是探讨早期地壳形成演化的关键地区。最近的地质调查工作,在泰安地区识别出一套变玄武岩组合。通过锆石U-Pb定年,获得侵入变玄武岩的奥长花岗岩脉年龄为2717±10Ma、二长花岗岩脉年龄为2549±15Ma,并在变玄武岩中获得~2729Ma、~2596Ma和2553~2549Ma多期年龄信息,由此确定变质玄武岩形成年龄大于~2.72Ga,遭受新太古代晚期~2.60Ga和~2.55Ga构造热事件影响。泰安地区变玄武岩组合归属于新太古代早期的泰山岩群雁翎关岩组。这些玄武岩遭受了后期(~2.55Ga)花岗质岩浆侵位作用的影响,并在原岩岩浆演化过程中经历了橄榄石和单斜辉石的结晶分离。变玄武岩为拉斑质玄武岩,显示出原始地幔一致的微量元素组成(Nb/Y=0.08~1.14、Nb/Th=1.82~13.4、Zr/Nb=17.9~27.2),表现为近平坦或弱分异的稀土元素配分模式[(La/Yb)N=0.90~2.52]和平坦的重稀土配分模式[(Gd/Yb)N=1.04~1.23];具有低的Sm/Yb比值(0.95~1.25)和正的εNd(t)值(2.48~3.64)。区域上,雁翎关岩组变玄武岩主要伴生科马提岩,成分均一,无伴生陆源沉积物,微量元素组成上与洋底高原玄武岩特征类似,来源于地幔柱头部尖晶石橄榄岩的部分熔融。新太古代早期(~2.7Ga),鲁西地区出现由科马提岩和拉斑玄武岩组成的绿岩带,同期出现新生的TTG陆壳,形成于地幔柱构造体制;新太古代晚期(~2.5Ga)出现钙碱性火山岩、TTG、赞岐岩和富钾花岗岩组合,显示出强烈的壳-幔相互作用和地壳物质再循环,板块构造体制已开始作用。综合地质资料揭示,华北克拉通构造体制在新太古代发生重大转变:由早期地幔柱逐渐转变为晚期的板块构造体制。
The western Shandong region preserves the most typical Neoarchean granite-greenstone belt of the North China Craton,with weak subsequent geological modification,making it a key area for exploring early crustal formation and evolution.Recent geological surveys in the Tai an area identified a suite of metabasalt assemblages.Zircon U-Pb dating determined the ages of the intruding trondhjemitic and monzogranitic veins to be 2717±10Ma and 2549±15Ma,respectively.Additionally,multiple age data of~2729Ma,~2596Ma and 2553~2549Ma were obtained from the metabasalts,indicating its formation age to be greater than~2.72Ga and was influenced by the Late Neoarchean~2.60Ga and~2.55Ga tectonic thermal events.The metabasalts in the Tai an area belong to the Early Neoarchaean Yanlingguan Formation,Taishan Group.These basalts were subjected to late(~2.55Ga)granitic magmatic emplacement and underwent olivine and clinopyroxene fractional crystallization during protolith magmatic evolution.They display tholeiitic basaltic composition,showing the same trace element composition as the primitive mantle(Nb/Y=0.08~1.14,Nb/Th=1.82~13.4,Zr/Nb=17.9~27.2),producing near-flat to weakly fractionated rare earth element(REE)distribution patterns[(La/Yb)N=0.90~2.52]and flat heavy REE slopes[(Gd/Yb)N=1.04~1.23],with low Sm/Yb ratios(0.95~1.25)and positiveεNd(t)values(2.48~3.64).Regionally,the metabasalts of the Yanlingguan Formation are mainly associated with komatiites with uniform composition and no associated terrigenous sediments.The trace element composition of metabasalts is similar to that of oceanic plateau basalts,derived from the partial melting of spinel peridotite at the plume head.During the Early Neoarchean(~2.7Ga),the western Shandong region developed a greenstone belt composed of komatiites and tholeiitic basalts,accompanied by juvenile tonalitic-trondhjemitic-granodioritic(TTG)continental crust,indicative of a mantle plume tectonic regime.In the Late Neoarchean(~2.5Ga),a combination of calc-alkaline volcanic rocks,TTGs,sanukites and potassium-rich granites emerged,reflecting strong crust-mantle interactions and crustal recycling,signifying the onset of plate tectonics.The comprehensive geological data reveal that the tectonic regime of the North China Craton underwent a significant transition during the Neoarchean,shifting from an early mantle plume to a late plate tectonic mechanism.
作者
张家辉
相振群
施建荣
初航
张健
陈春晖
丁海洋
李怀坤
ZHANG JiaHui;XIANG ZhenQun;SHI JianRong;CHU Hang;ZHANG Jian;CHEN ChunHui;DING HaiYang;LI HuaiKun(Tianjin Center,China Geological Survey(North China Center for Geoscience Innovation),Tianjin 300170,China;Precambrian Geological Research Center,China Geological Survey,Tianjin 300170,China;Shandong Yuqiang Geological Resource Exploration and Development Co.,LTD,Tai an 271000,China;Management Committee of Taishan Scenic and Historic Area,Tai an 271000,China)
出处
《岩石学报》
SCIE
EI
CAS
CSCD
北大核心
2024年第11期3336-3362,共27页
Acta Petrologica Sinica
基金
中国地质调查局项目(DD20240027)
泰山风景名胜区管理委员会项目(SDGP370997202002000007)
国家自然科学基金项目(U2244211、41902196)
国家重点研发计划项目(2023YFF0803802)联合资助
关键词
花岗-绿岩带
新太古代
地球化学
泰山岩群
鲁西
Granite-greenstone belt
Neoarchean
Geochemistry
Taishan Group
Western Shandong
