西北地质
西北地質
서북지질
NORTHWESTERN GEOLOGY
2014年
3期
1-7
,共7页
北祁连%基性岩墙%早二叠世%伸展裂解
北祁連%基性巖牆%早二疊世%伸展裂解
북기련%기성암장%조이첩세%신전렬해
north Qilian Mountains%basic dyke%Early Permian%extension and collapse
在玉龙滩地区古元古代托赖岩群变质岩中发现了一套基性岩脉侵入体,岩石类型主要为辉长岩、辉绿岩,侵入于托赖岩群片麻岩、片岩,岩脉长轴走向大多以北西向为主,个别近南北向或北东向,露头规模一般长10~35 m,宽5~10 m。通过同位素测年分析辉绿岩脉地质时代为早二叠世,结合对地质特征、岩石学特征、岩石化学、地球化学特征的研究,认为其属于拉斑玄武系列,形成于伸展性构造环境。结合本区区域地质分析,该岩脉可能为祁连山造山带加里东期造山运动结束之后,由于陆壳加厚而发生伸展崩塌,造成幔源基性岩浆底侵,形成了该类相当于基性岩墙的产物。反映北祁连地区在早二叠世有一期陆壳加厚伸展背景下的基性岩浆底侵事件。
在玉龍灘地區古元古代託賴巖群變質巖中髮現瞭一套基性巖脈侵入體,巖石類型主要為輝長巖、輝綠巖,侵入于託賴巖群片痳巖、片巖,巖脈長軸走嚮大多以北西嚮為主,箇彆近南北嚮或北東嚮,露頭規模一般長10~35 m,寬5~10 m。通過同位素測年分析輝綠巖脈地質時代為早二疊世,結閤對地質特徵、巖石學特徵、巖石化學、地毬化學特徵的研究,認為其屬于拉斑玄武繫列,形成于伸展性構造環境。結閤本區區域地質分析,該巖脈可能為祁連山造山帶加裏東期造山運動結束之後,由于陸殼加厚而髮生伸展崩塌,造成幔源基性巖漿底侵,形成瞭該類相噹于基性巖牆的產物。反映北祁連地區在早二疊世有一期陸殼加厚伸展揹景下的基性巖漿底侵事件。
재옥룡탄지구고원고대탁뢰암군변질암중발현료일투기성암맥침입체,암석류형주요위휘장암、휘록암,침입우탁뢰암군편마암、편암,암맥장축주향대다이북서향위주,개별근남북향혹북동향,로두규모일반장10~35 m,관5~10 m。통과동위소측년분석휘록암맥지질시대위조이첩세,결합대지질특정、암석학특정、암석화학、지구화학특정적연구,인위기속우랍반현무계렬,형성우신전성구조배경。결합본구구역지질분석,해암맥가능위기련산조산대가리동기조산운동결속지후,유우륙각가후이발생신전붕탑,조성만원기성암장저침,형성료해류상당우기성암장적산물。반영북기련지구재조이첩세유일기륙각가후신전배경하적기성암장저침사건。
A set of basic dyke intrusion has been found in metamorphic rocks of Tuolai Paleoproterozoic rock group in Yulongtan Region.Gabbro vein and diabasic dyke are found to be the main intrusive rocks and they intruded into the gneiss and schist of Tuolai rock group.The axes of the dykes are mostly NW,with a few close to SN or NE,the outcrop scale is within 10-35m in length and 5-10m in width.Isotope dating analysis on diabasic dyke shows its geological age as early Permian.Combined with its geological features,petrology,petrochemistry and geochemistry characteristics,it is suggested that the dyke belongs to tholeiitic series and forms in extensional tectonic setting.Considering the regional geological analysis,it is concluded that after Caledonian orogeny,Qilianshan orogenic belt had experienced a stretch and collapse due to the thickening of continental crust,and the process led to the underplating of basic mantle-derived magma,thus formed the basic dyke.It is reflected that in early Permian a basic magma underplating event occurred with continental crust thickening and extension in north Qilian area.
