作　　者： ; ; ;

机构地区： 成都理工大学地球科学学院

出　　处： 《矿物岩石》 2013年第3期54-62,共9页

摘　　要： 从岩石学和主微量元素地球化学的角度对山东胶南燕山期碱性正长岩进行研究,结果表明:该正长岩的w(SiO2)为63.28%～64.66%,w(K2O)为5.62%～6.08%,K2O/Na2O>1,w(Na2O+K2O)为10.20%～11.05%,为准铝质(其中w(Al2O3)=16.84%～17.23%,A/KNC=0.96～0.98),属于碱性正长岩;相对富集轻稀土而亏损重稀土,具有较弱的负Eu异常(δEu=0.73～0.85),富集大离子亲石元素(Rb,Ba)、Th和U,相对亏损高场强元素(Nb,Ta,Zr,Hf,Ti,P)。研究表明,该碱性正长岩为富集岩石圈地幔部分熔融的产物,但在成岩过程中可能经历了钾长石、斜长石、磷灰石、Ti-Fe氧化物、角闪石和黑云母等矿物的分离结晶作用,该正长岩形成于岩石圈拉张减薄的构造环境,岩浆在上升侵位过程中没有受到明显地壳物质的混染。 Petrological and geochemical studies are carried out for the Yanshanian alkaline sye- nites from Jiaonan of Shandong Province, and the petrogenesis of these rocks are discussed. It shows that the w（SiO2） contents of the syenites vary from 63.28% to 64.66% ,and are character- ized by highw（K20） （5. 62%-6. 08%） and w（Na2O＋K2O） contents 10.20%-11.05%,be- longing to metaluminous rocks and alkaline series. Chondrite-normalized patterns for the syenites exhibit moderate depletion in HREE,as well as moderate negative Eu anomalies （δEu=0.73- 0.85） ;and the primitive mantle-normalized spidergrams show relatively enrichment in the LILE （Rb,Ba）, Th and U, but depletion in the HSFE （Nb, Ta, Zr, Hf, Ti and P）. It is considered that these alkaline rocks were derived from partial melting of the enriched lithospheric mantle in the extensional tectonic setting. Meanwhile, the parental magma underwent intense mineral fractional crystallization, such as potassium feldspar, plagioclase, apatite, hornblende and biotite, whereas there have no obvious crustal contamination during magma ascent.

关 键 词： 岩石成因 地球化学 碱性正长岩 燕山期 胶南 山东

领　　域： [天文地球] [天文地球] [天文地球] [天文地球]