摘要
苏北东海地区主侵入花岗岩类岩石属Ⅰ型花岗岩类。其主要造岩矿物为阳起角闪石、富镁黑云母、更长石、钾长石和石英。主要副矿物为榍石、磷灰石、锆石、磁铁矿等。主侵入岩体的形成温度为910—690℃,logfo_2=-12,fH_2O=(1.3—1.8)×10~8Pa,log(fH_2O/f_(HF))=3—4。第一类过渡元素富集于角闪石、黑云母和榍石中,而在更长石、钾长石和石英中明显亏损。由于榍石、角闪石、黑云母和更长石对全岩REE含量的贡献最大,因此它们控制了本区花岗岩类岩石的稀土配分模式。前三者富重稀土,负Eu异常较强,斜长石相对富轻稀土,并表现为正Eu 异常。因此可以认为随着花岗质岩浆中铁镁矿物和斜长石的分离,将会导致残余岩浆中第一类过渡元素、重稀土元素和Eu的亏损。
The quartz monzonite-monzonitic granite masses are the main intrusive products in Donghai area, northern Jiangsu and can be classified as I-type granitoids. The major rock-forming minerals are composed of actinolitic hornblende, Mg-rich biotite, oligoclase, perthite and quartz, with sphene, apatite, zircon, magnetite etc. as chief accessories. The thermodynamic calculation indicates that the physicochemical crystallization conditions of the magma are t=910-690℃, logfo_2=-12, fH_2o=(1.3-1.8)×10~8Pa and log(fH_2o/fHF)=3-4. The lst set of transition elements are abundant in hornblende, biotite and sphene, but are obviously reduced in oligoclase, perthite and quartz. As hornblende, biotite and oligoclase play the most important part in the contribution of REE contents to the whole rocks, they control the REE distribution patterns of the rocks. These three minerals are usually rich in HREE with comparatively large negative Eu anomaly, while plagioclase is relatively rich in LREE and exhibits positive Eu anomaly. Thus, with the advance of magmatic fractionation, the marie minerals and plagioclase will be gradually separated from each other, and this will lead to the depletion of HREE, transition elements of lst set and Eu contents.
出处
《岩石矿物学杂志》
CAS
CSCD
1989年第2期163-172,共10页
Acta Petrologica et Mineralogica
关键词
花岗
岩类岩石
矿物
地球化学
granitoids
geochemistry of minerals, northern Jiangsu
