香格里拉洛吉晚二叠系玄武岩的元素地球化学及其成因研究  

ELEMENTAL GEOCHEMISTRY AND PETROGENESIS OF PERMIAN BASALTS IN LUOJI,SHANGRI-LA

作　　者：王涛[1,2] 肖渊甫[1] 邓江红[1] 吕劲松[1] 于海军[1] 

机构地区：[1]成都理工大学地球科学学院,四川成都610059 [2]中国科学院地球化学研究所矿床地球化学国家重点实验室,贵州贵阳550002

出　　处：《矿物岩石》2012年第4期41-51,共11页Mineralogy and Petrology

基　　金：中国地调局(1212011120587);国家自然科学基金(41103017);四川省重点学科基金(SZD0407);矿床地球化学国家重点实验室开放基金(201105)

摘　　要：从矿物学和主微量元素地球化学的角度对香格里拉洛吉玄武岩进行研究。该玄武岩的w(SiO2)为45.08%～50.50%,w(MgO)为2.86%～14.73%,w(Na2O+K2O)为1.78%～6.34%,且Na2O>K2O,属于碱性玄武岩系列;相对富集轻稀土而亏损重稀土(LREE/HREE=1.88～9.61),轻重稀土发生了一定程度的分异,没有明显的Eu异常(δEu=0.91～1.10),富集大离子亲石元素(Rb,Ba,Sr,Pb),相对亏损高场强元素(Nb,Ta,Zr,Hf),且表现出Pb的强烈富集,Ba和Sr元素有明显的波动。研究表明,该玄武岩为富集岩石圈地幔石榴石+尖晶石二辉橄榄岩5%～20%部分熔融的产物,形成于板块汇聚边缘的构造环境,在成岩的过程中不存在明显的地壳混染,并且发生了橄榄石、单斜辉石、磷灰石、金红石的分离结晶作用。The basalt occurred in the Luo]i area of Shangri-la County is studied in the aspects of their petrology and geochemistry and its petrological genesis is discussed. It is showed that the w （SiO2） contents of the basalts vary from 45. 08% to 50.50% ,and characterized by high w（MgO） （2.86%-- 14.73M） and w（Na2O＋ K2O） contents 1.78 %~ 6.34% （Na2O〉 K2O）, suggesting that these rocks belong to alkaline basalt series. Chondrite-normalized patterns for the basalts ex- hibit flat but moderate depletion in HREE （LREE/HREE-----1.88~9.61） without Eu anomalies （SEu= 0. 91~1.10）, and the primitive mantle-normalized spidergrams show relatively enrichment in the LILE （Rb,Ba,Sr,and Pb）,but depletion in the HSFE （Nb,Ta,Zr and Hf）,with obvious wave of Ba and Sr. Based on the above geochemical features,it is proposeg that these hasalts were derived from partial melting （5 % ~20 %） of the enriched lithospheric mantle of the garnet-spinel mantle peridotites in the tectonic setting of convergent plates. Meanwhile, the parental magma experienced intense mineral fractional crystallization, including olivine, clinopyroxene, apatite and rutile. Meanwhile t weak crustal contamination occurred during magma ascent.

关 键 词：地球化学 岩石成因 玄武岩 晚二叠系 洛吉 香格里拉 

分 类 号：P581[天文地球—岩石学] P595[天文地球—地质学]