摘要
华北克拉通北缘西段中元古代花岗岩类仅见于查干础鲁-霍尔森构造带以南的雅布赖-巴音诺尔公构造带中,整体上受NEE向长寿命线性构造控制。据岩性可分为斜长花岗岩和石英闪长岩两类。斜长花岗岩为S型花岗岩,但具有向I型过渡的特征,富含Cr、Ni、SiO2、Al2O3,其均值分别为672μg/g、405μg/g、71.40％和14.93％,δEu值变化大,介于0.34和3.95之间,起源于幔源岩浆与壳源物质的混合。石英闪长岩为典型的I型花岗岩,其Cr、Ni含量的均值分别为220μg/g和162μg/g,类似于华南同熔型花岗岩。斜长花岗岩中的锆石U-Pb等时线上交点年龄为1256Ma,代表了发生于华北克拉通北缘西段的一次构造-热事件。伴随这一构造-热事件,华北克拉通北缘西段发生拉伸裂解,进入拉张型过渡壳阶段。中元古代花岗岩类是这一构造热事件的重要产物。在这一构造-热事件中,推测查干础鲁-霍尔森一线地壳减薄最大,其北侧的宗乃山-沙拉扎山构造带因无同时代岩浆作用,为非火山型被动陆缘,南侧的雅布赖-巴音诺尔公构造带广泛发育了花岗岩类、镁铁质、超镁铁质侵入岩,以及火山-沉积组合,为火山型被动陆缘,二者构成被动陆缘“对”。
The Mesoproterozoic granitoid rocks in western section of northern margin of the North China craton are only distributed in Yabulai-Bayinlergong Tectonic Belt in the south of the Caganchulu-Houershen Tectonic Belt, being controlled generally by NEE striking long-living linear structure, and can be classified into two types by rock facies. plagiogranite and quartz diorite. Plagiogranite is S-type granite, having higher Cr, Ni, SiO2 and Al2O3 of 672 mug/g, 405 mug/g, 71.40% and 14.93% respectively on the average and large variation of delta Eu (0.34 similar to 3.95), with some character of I-type. These characteristics of the rocks mean that they originated from mixing of mantle-genesis magma and crust-genesis material. Quartz diorite is typical I-type granite, having higher Cr, Ni contents, of 220 mug/g and 162 mug/g respectively on the average, and similar to co-melting granites of Southern China. The upper intercept of U-Pb zircon isochron dating yielded an age of 1256Ma for plagiogranite representing an important thermal-tectonic event in western section of northern margin of North China craton. Accompanied by this thermal-tectonic event, there were extending and spreading in the area, and developed into the evolving stage of extensional type of transitional crust. Mesoproterozoic granitoid rocks were the important products of the thermal-tectonic event. It is speculated that the crust of the Caganchulu-Huoershen Tectonic Belt were thinned greatly during that event. There was no magmatism of the era in the Zhunleishan-Shalazhashan Tectonic Belt, north of the linear structure, so it is called nonv-olcanic passive continental margin. Because there were granitiod rocks, mafic, ultramafic intrusion rocks, and volcanic-sedimental assemblage of Mesoproterozoic in the Yabulai-Bayinlergong Tectonic Belt, the belt is called volcanic passive continental margin. Both of the margins constituted the passive continental margin 'couple'.
出处
《岩石学报》
SCIE
EI
CAS
CSCD
北大核心
2001年第4期609-616,共8页
Acta Petrologica Sinica
基金
国家自然科学基金(编号:49572152)资助项目.
关键词
拉张型过渡壳
地球化学
花岗岩
华北克拉通
中元古代
构造环境
transitional crust of extensional type
geochemistry
granitoid rocks
western section of northern margin of
the North China craton
