摘要
吉林省南部辉南-靖宇地区第四纪碱性玄武岩中的地幔包体主要为尖晶石相二辉橄榄岩和方辉橄榄岩。二辉橄榄岩和方辉橄榄岩的平衡温度分别为770～1000℃和850～1025℃,对应的氧逸度(fO2)值分别为FMQ-0.70至+0.34(均值为FMQ-0.06)和FMQ-0.46至+0.05(均值为FMQ-0.15),它们与深海橄榄岩(abyssal peridotites)以及软流圈地幔的fO2相似。橄榄岩的fO2值,连同其全岩化学成分(如Mg#、Al2O3、CaO、Ni、Co和Cr)和矿物化学成分(如橄榄石的Fo、尖晶石的Cr#和Mg#,以及辉石的Mg#)特征,表明辉南-靖宇地区龙岗火山群下面的岩石圈地幔很可能是在晚中生代以来,伴随着华北克拉通和扬子板块的碰撞以及来自东侧太平洋板块和北侧蒙古-额霍次克(Mongolo-Okhotsk)板块分别向西和向南的俯冲叠加,原来的古老岩石圈失衡、塌陷(拆沉?),取而代之的深部软流圈底辟、上涌,又经历了低度部分熔融的产物。
The mantle xenoliths in the Quaternary basalts in Huinan-Jingyu area,southern Jilin Province,China,comprise mainly spinel-facies lherzolites and harzburgites.The equilibration temperatures for lherzolites and harzburgites are 770~1000℃ and 850~1025℃,and the calculated fO2 values are in the range of FMQ -0.70 to ＋0.34 and FMQ -0.46 to ＋0.05,respectively,which are similar to those for abyssal peridotites and asthenospheric mantle.The fO2 values of peridotites,together with their bulk rock compositions （e.g.,Mg#,Al2O3,CaO,Ni,Co,Cr） and mineral compositions （e.g.,Mg# of olivine and pyroxene,Cr# and Mg# of spinel）,suggest that the present-day lithospheric mantle beneath Longgang volcanic field represents an upwelling asthenospheric mantle formed in response to the imbalance and delamination of an old lithosphere caused by the collision between North China craton and Yangtze plate,accompanied by the multiple subductions of Pacific plate from the east and Mongolo-Okhotsk plate from the north since Late Mesozoic time.The newly formed mantle beneath the area has undergone a low degree of partial melting which led to the formation of the observed lithologies.
出处
《岩石学报》
SCIE
EI
CAS
CSCD
北大核心
2011年第6期1797-1809,共13页
Acta Petrologica Sinica
基金
国家自然科学基金项目(40873016
41072249
90814003)
加拿大NSERC项目联合资助
