摘要
下地壳拆沉是人们关注的问题,文中指出下地壳拆沉必须满足至少三个条件：(I)地壳加厚使其下部达到榴辉岩相是拆沉的前提。(2)大规模岩浆活动使大量低密度的中酸性物质移出下地壳,使下地壳密度增加直至超过下伏地幔。由于下地壳榴辉岩相岩石部分熔融所形成的岩浆具有埃达克岩的地球化学特征,因此,大规模埃达克岩的熔出是下地壳拆沉的先决和必要条件。(3)岩石圈地幔转化为软流圈地幔,使下地壳能够进入地幔。陆壳下的岩石圈地幔原先是冷的、刚性的和不易流动的,如果有热和水的加入,可以被软化,使其变成热的、塑性的和易流动的软流圈地幔。因此,岩石圈地幔转化为软流圈地幔是下地壳拆沉的必要和充分条件。作者认为,下地壳不大可能整体拆沉,而很可能是一块一块如飘雪花似地拆沉。如果下地壳的密度降低(低于下伏地幔),如果地幔停止热的供给,如果陆壳底部的软流圈地幔又恢复为岩石圈地幔,拆沉即终止。文中讨论了中国东部中生代下地壳拆沉的可能性,探讨了岩石圈减薄的机制,认为下地壳不需要也不可能与岩石圈地幔一道拆沉。
It is the subject that pcople pay attention to contiental lower crut delaminattion,The paper puts out that there are at least three conditions fox lower crust delamination：（1）the thickaned crust is the prerequisite that the delamination ruake the lower crust eclogitc.（2）the exlensive umgma shifts out a lerge amount of low density acid magma,cnables the crust density to be greater than the mantle density.Because the lower crust enlogltalion and some magma melting are of the geochemistry characteristics of adakite ,the lower crust dolamination is the prerequisite and essential condition with the extensive adukite melted out .（3）that the lithosphere mantle transfers into the asthenoshpere mautle cnsbles the lower crust into muntle.The mantle under continent crust is cold and rigidity originally,difficult to flow,and will be soften with beut and water Joining ,muke into the asthcnnsphore heat,plasticity and ,easy flow.So that the transition between the litiosphere mantle and the asthonosphere antle is the essential faclor and precoodition of the lower cnist delamination.The anthor thinks that the crust will not delaminate a wholly、otherwise,it will delaminate as the anow flake float probably.If the density of the lower crust is reduced（lower than the underlying manthe）,and there is not hcat supply in mantle ,and the asthenosphere under continent crust tuat into the Jithosphere mantle again,delsmination will atop promplly.In the article we disoussed the possibility of lower arust delamination in the eastern China during Mesozoic Era、and the thinning mechanism of the lithosphere.We think that the lower crust is not necessary ,is not possible to delaminate together with the lithosphere manile as well.
出处
《岩石学报》
SCIE
EI
CAS
CSCD
北大核心
2006年第2期265-276,共12页
Acta Petrologica Sinica
基金
中国科学院知识创新工程基金(KZCX 1-07和KZCX2-SW-119)资助的项目。
关键词
大陆下地壳
拆沉作用
埃达克岩
岩石圈地幔
软流圈地幔
Contincntsl lower orust
Delamination
Adakite
Lithospheric mantlc
Ashoapherie mantle
