| 中国泥盆纪鲕铁石沉积环境、成因 |
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| 引用本文： | 廖士范,魏梁鸿.中国泥盆纪鲕铁石沉积环境、成因[J].沉积学报,1993,11(1):93-102. |
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| 作者姓名： | 廖士范 魏梁鸿 |
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| 作者单位： | 1.贵州省地矿局; |
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| 基金项目： | IGCP277 POI(显生宙鲕铁石)研究项目 |
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| 摘 要： | 中国泥盆纪鲕铁石分布在华南的云南、四川、贵州、广西、湖南、江西、湖北等7个省(区)。鲕铁石结构有鲕粒、假鲕粒、凝胶团粒。鲕粒一般有环带、有核心,也有仅有环带、无核心的鲕环2-3层,少数数十层。鲕粒环带、团粒一般为自形晶微粒赤铁矿、绿泥石、菱铁矿,含少量粘土矿物及其他自形品矿物。核心为石英碎屑,或铁矿物碎屑。鲕粒间基质自形晶矿物、粘土矿物及其碎屑矿物。以接近封闭的浅水泻湖环境沉积最好(占鲕铁石总储量60%),以河口三角洲砂坝沉积最差(占4.2%)。鲕铁石是海水中胶体沉积的,当海水有一定能量时,铁质围绕碎屑物或铁矿物碎屑转动沉积鲕粒环带,铁质也可围绕先凝聚的铁矿物转动沉积无核心的环带。当海水能量低时形成凝胶团粒。
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| 关 键 词： | 鲕铁石 鲕粒环带 鲕粒核心 |
| 收稿时间： | 1991-03-16 |
Sedimentary Environments and Origin of the Devonian Oolitic Ironstones in China |
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| Institution: | 1.Guizhou Bureau of Geology and Mineral Resources |
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| Abstract: | There are 7 minerogenetic districts of middle Devonian, the important ones are the I ,II , III and IV .. and of late Devonian, V, VI, and VII. Generally, there are 2-3 girdles in one oolite, but sometimes the number can as large as 20 and as small as one , the later may be called the pseudoolites. Sometimes an oolite is a gel cumularspharolith without girdles and without nucleus and sometimes there are many girdles in oolites but without nucleus. Composition of the girdles of oolites and gel cumularspharolithes are automorphic crystals of micrograined hematite, chlorites, siderites or the mixture of the three minerals with some clay minerals (mainly is illite) , minute collphane. The nuclei are made of quartz debris in general. The matrix between oolites are made of automorphic crystal micrograined ferruginous minerals, clay minerals, minute collphane or their clastes and quartz clastes. Oolites, pseudoolites, cumularspharolithes are round, ellipsoidal in shape, 0.2-0.8mm in diameter, and all of them are in the same size. The content of oolitic ironstone TFe is 30-40% generally with the range of 27-28% to 40-46%. In China, the best sedimentary environment of Devonian oolitic ironstone is the region nearby the closed shallow water lagoon , where reserved 60% of total Devonian ollitic ironstone, the worst is the river mouth delta sand shoal, in which the ore reserve is small (only 4.2%) and ore is poor (TFe27-28) . The precursor of the oolites girdles is colloid deposits in sea water, under the condition of high energy water, the ferrugenous materials around the debris or the former colloid segration of micrograined authigenous ferro-minerals will rotate and deposite and form the girdles of ironstone oolites. Under this condition there are muclei girdles in ironstone oolites, but some oolites without nuclei only with girdles. When the sea water only with a lower energy, the gel cumularspharolith without nucleus and without girdles may be deposited. |
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