江西安远路迳金伯利质煌斑岩筒研究——一种新型的幔源碱性超基性岩  

PPAEGSS Research on kimberlitic lamprophyre pipe at Lujing in Anyuan area,Jiangxi Province——A new type of mantle-derived alkaline ultrabasic rock

作　　者：叶松[1] 杨眉[1] 叶德隆[1] 邰道乾[1] 任迎新[1] 

机构地区：[1]中国地质大学,武汉430074

出　　处：《矿产与地质》2007年第4期383-394,共12页Mineral Resources and Geology

基　　金：国家自然科学基金项目(批准号49672105)资助

摘　　要：路迳岩筒属火山通道相,由金伯利质煌斑岩、角砾岩、角砾凝灰岩组成,富含幔源橄榄岩包体、普通辉石巨晶和岩球。造岩矿物是橄榄石、斜方辉石、单斜辉石、角闪石和金云母,深源特征指示矿物有镁铝榴石、铬透辉石、铬尖晶石和镁钛铁矿。岩石化学组成超低SiO2,低MgO,高Al2O3,富碱,富挥发组分。轻稀土元素富集,相容元素贫化,不相容元素明显富集。岩浆起源深度约85km。其中:岩体产状,富含包体、巨晶和岩球,岩石结构和构造,矿物组成,岩石化学组成超低SiO2、富碱、富挥发组分等特征与金伯利岩相似;但岩石化学组成高Al2O3,低MgO,K2O低于Na2O,REE和LREE/HREE偏低,部分微量元素的亏损或富集,金云母成分富TiO2,富TFeO,贫MgO,镁铝榴石、铬透辉石、铬尖晶石和镁钛铁矿的Cr2O3含量偏低,岩浆起源深度较浅,均与金伯利岩有重大差异,而更接近煌斑岩类。研究认为,是幔源岩浆岩的一种新类型,岩石名称界定为金伯利质煌斑岩。The Lujing pipe is a volcanic channel, composed of kimberlitic lamprophyre, volcanic breccia and breccia-tuff with rich mantle-derived lherzolite xenoliths, augite megacrysts and rock nodule in it. The diagenetic minerals are olivine, orthopyroxene, clinopyroxene, amphibole and phlogopite, and the deepsource characteristic indicating minerals are pyrope, chrome-diopside, chrome-spinel and magnesioilmenite. The petrochemical composition is as followings： ultra-low SiO2, low MgO, high Al2O3, enriched alkali and volatiles with LREE being enriched, whereas the compatible element being depleted while the incompatible element being distinctly enriched. The magma originated from a deep source at about 85 kin. The rock occurrence, richness of xenoliths, megacrysts and rock nodule, the texture and structure of the rock, the compositions of the minerals, ultra-low SiO2, enriched alkali and volatiles, etc. , all these features show some similarity to those of kimberlite. However, high Al2O3, low MgO, lower content of K2O than that of Na2O, REE and LREE/HREE on the low side, the depleted or enriched degree of some trace element, the high TiO2 and TFeO but low MgO in phlogopite, the content of Cr2O3 in pyrope, chrome-diopside, chrome-spinel and magnesioilmenite on the low side mean that the magma was originated from more shallow sources, all these are very different from the kimberlitic features, but closer to the features of lamprophyres. It is believed that the rock studied is a new type of mantle-derived igneous rock and should be defined as kimberlitic lamprophyre.

关 键 词：超基性岩 新类型 金伯利质煌斑岩 碱性超基性岩 岩筒 幔源包体 高压巨晶 岩石化学和矿物化学 江西安远 

分 类 号：P618.7[天文地球—矿床学]