Petrogenesis of katungite and its associates
Petrogenesis of katungite and its associates
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卡钨矿及其伴生岩石的成因
DOI：
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发表时间：
1950
期刊：
影响因子：
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通讯作者：
A. Holmes
中科院分区：
文献类型：
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作者：
A. Holmes
Ruwenzori附近的年轻火山岩区的特征是由黄长石和/或普通辉石、六方钾长石和/或白榴石和/或富钾玻璃的各种组合组成的超基性钾质火山岩;除少数例外，还有橄榄石;不变的附件是钙钛矿和黑色矿石。类型包括katungile（橄榄石黄长石富钾玻璃），maJurita（橄榄石 *Augitefkalsilite），和ugandite（橄榄石Augitefleucite）和所有可能的过渡代表。这一活动具有强烈的爆炸性。火山碎屑中总是含有基底岩石和由辉石和/或黑云母和/或橄榄石（O. B. P.系列）组成的同源次火山岩套的碎片。后者的岩石和矿物与凝灰岩中的碎屑和火山岩中的包裹体等火山类型相似。表明原卡吞岩（无橄榄）-卡吞岩-阿尼基特 * 橄榄-乌阿奇岩系列是一个成因系列，可能是由比原卡吞岩更超基性的岩浆物质从O. B. P.形成的。在较早的假说中，这种岩浆物质被认为是由碱金属和钙离子组成的“射气”（E），但“射气”和O. B. P.岩石的来源却没有得到解释。现在有人提出，碱铝物质（以及由此产生的岩石中的所有SiOg）来自花岗岩（G）及其衍生物，而钙质物质来自“岩浆碳酸岩”（C）。对于katunion（K），假设可以用C*G：O. B. P. * 的形式表示。K.额外的钾碱（例如在镁铁矿中）是由于在更深处形成的黑云母被蚀变并将其部分钾碱释放到液相中这一已证实的事实。简要地提到了“岩浆碳酸岩”假说可能的应用：（o）富钠碱性岩石的岩石成因;和（B）非洲裂谷地区长期持续的隆升和裂谷本身的起源。
The young volcanic fields near Ruwenzori are characterised by ultrabasic potassic volcanic rocks made up of various combinations of melilite and/or augite; kalsilite and/or leucite and/or potash-rich glass; and, with few exceptions, olivine; invariabie accessories are perovskite and black ores. The types include katungile (olivinetmelilitefpotash-rich glass), maJurita (olivine*augitefkalsilite), and ugandite (olivinefaugite*leucite) and all possible transitions are represented. The activity was intensely explosive. The pyroclasts invariably contain fragments both of basement rocks and of a cognate sub-volcanic suite composed of pyroxene and/or biotite and/or olivine (O.B.P. series). Tihe rocks and minerals of the latter appear simultaneousiy with the volcanic types as fragments in the tuffs and inclusions in the lapilli, etc. It is shown that the series proto-katungite (olivinefree)-katungite-alnijit*olivine-ouachitite is a genetic one that could have been formed from O.B.P. by magmatic material even more ultrabasic than proto-katungite. In an earlier hypothesis this magmatic material was regarded as "emanations" (E) of alkaiuminous and cafemic composition, but the sources of the "emanations" and of the O.B.P. rocks were then left unexplained. It is now suggested that the aik-aluminous material (and all the SiOg of the resulting rocks) came from granite (G) and its derivatives, and that the cafemic material came from "magmatic carbonatite" (C). For katungite (K) the hypothesis can be expressed in the form C*G:O.B.P.*K. Additional potash, (e.g. in mafurite) is accounted for by the demonstrated fact that biotite formed at greater depths became altered and gave up part of its potash to the liquid phase. Brief reference is made to the possible appiication of the "magmatic carbonatite" hypothesis (o) to the petrogenesis of soda-rich alkali rocks; and (b) to the long-continued uplift of the rift valley regions of Africa and the origin of the rifts themselves.