金伯利岩:地球深部探测的重要探针

Kimberlites: Important Probes for Deep Earth Exploration

金伯利岩是一种偏碱性的超基性岩,来源于地幔深部,富含挥发份和钾质,属于火成岩类,金伯利岩中主要含有镁铝榴石、金刚石、橄榄石、铬铁矿、铬透辉石、镁钛铁矿,锆石、碳硅石等造岩矿物。同时金伯利岩也被认为是含金刚石最主要的岩石。本文通过文献调研方法,野外现场表明金伯利岩中含有深源包裹体;全球金伯利岩主要分布在俄罗斯、博茨瓦纳、加拿大、安哥拉、南非、刚果民主和纳米比亚;中国金伯利岩主要分布在华北地台,在山东、辽宁、吉林、山西、河南和新疆等地。这些金伯利岩常常与深大断裂甚至地幔深部地质作用关系密切,常出现标志性矿物橄榄石、石榴石、高铬磁铁矿,伴有烃类或氢气。但含金刚石金伯利岩主要沿郯庐断裂带分布,如辽宁瓦房店、山东蒙阴等地。从时代上看,以往认为的早古生代的金伯利岩,更可能都是在早期形成于华北地台之岩石圈底部,而在中生代白垩纪时期才在大规模岩石圈拆沉的地质背景下的以快速上升的,尤其是那些含金刚石的金伯利岩岩管更是快速上升的典型代表,其标型矿物是镁铝榴石、高铬磁铁矿、钙钛矿等。国内辽宁瓦房店含金刚石金伯利岩产于郯庐断裂带东侧,有着与同期金伯利岩相同的岩石矿物学特征,其中的以50号岩管为代表的金刚石矿床是我国重要的战略矿产。金伯利岩及其中的金刚石带来众多直接的深部地幔信息,中国瓦房店、蒙阴一带的金刚石来自上地幔,而一些含硼蓝色金刚石则来自下地幔,不同层圈的金刚石携带不同的标志矿物,以橄榄石为例:来自上地幔金刚石携带的橄榄石为橄榄石;过渡带金刚石携带的主要为瓦兹利石和林伍德石;下地幔的金刚石则为布里奇曼石,它们是深部探测的重要探针。

Kimberlite is a kind of alkaline ultrabasic rock, derived from the deep mantle, rich in volatile and potassium, belonging to igneous rocks. Kimberlite mainly contains magnesium aluminum garnet, diamond,olivine, chromite, chromium diopside, magnesium ilmenite, zircon, carbonsilica and other rock forming minerals.Kimberlite is also considered to be the most important diamond-bearing rock. In this study, through literature research, the field shows that kimberlite contains deep-source inclusions. Kimberlite is mainly distributed in Russia, Botswana, Canada, Angola, South Africa, Democratic Republic of Congo and Namibia. Chinese kimberlites are mainly distributed in the North China Platform in Shandong, Liaoning, Jilin, Shanxi, Henan and Xinjiang. These kimberlites are often associated with deep faults and even deep mantle processes, often producing signature minerals such as olivine, garnet, magnetite, hydrocarbons, or hydrogen. However,diamond-bearing kimberlite is mainly distributed along the Tan–Lu fault zone, such as Wafangdian in Liaoning Province and Mengyin in Shandong Province. Look from age, ever think of early Paleozoic kimberlite and more were probably formed in early in the bottom of the lithosphere of north China platform, and in the Mesozoic cretaceous period under the background of large-scale lithosphere delamination geological with rapidly rising,especially those containing diamond kimberley intermediated-acidic tube is a typical representative of the rapid rise, The standard minerals are magnesium aluminum garnet, high chromium magnetite, perovskite and so on.The Wafangdian diamond-bearing kimberlite in Liaoning province is produced in the east of Tan–Lu fault zone and has the same petrological and mineralogical characteristics as the kimberlite of the same period. Among them,the diamond deposit represented by no. 50 rock pipe is an important strategic mineral in China. Diamond in kimberlite and many deep mantle information directly, brought Chinese Wafangdian diamond, darkened area from the upper mantle, while some boron blue diamond from the lower mantle, a sign of different layers of diamond with different minerals, olivine, for example: from the upper mantle diamond carry olivine olivine;The diamonds in the transition zone are mainly Wazilite and Ringwood stone. Bridgeman’s diamonds in the lower mantle are important probes for deep exploration.