| 苏皖坡缕石粘土中蛋白石特征及其成因意义 |
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| 引用本文： | 陈天虎,徐晓春,XU Hui-fang,岳书仓.苏皖坡缕石粘土中蛋白石特征及其成因意义[J].矿物学报,2005,25(1):81-88. |
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| 作者姓名： | 陈天虎 徐晓春 XU Hui-fang 岳书仓 |
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| 作者单位： | 1. 合肥工业大学,资源与环境工程学院,安徽,合肥,230009
2. 新墨西哥大学 地球与行星科学系, NM 87131, USA |
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| 基金项目： | 国家自然科学基金项目(批准号:40072017，40331001) |
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| 摘 要： | TEM和XRD研究表明，在苏皖坡缕石粘土矿床的蛋白石坡缕石层中存在0pal-A和0pal-CT两种结构的蛋白石。蛋白石坡缕石层主要含坡缕石、opal-A、opal-CT，以及少量白云石和其它矿物，由富opal-A层和富opal-CT层互层组成，交互层的厚度在几个厘米左右。蛋白石坡缕石层中的矿物基本是自生矿物，从蒸发湖水中化学沉淀形成。矿物组成特征研究表明，蛋白石坡缕石层的矿物组分(Si、Mg、Al)来源于盆地周围玄武岩淋滤的浅层地下水。根据Opal-A和Opal-CT溶解度图解和城缕石、白云石形成物理化学条件图解，当湖水具有高浓度溶解SiO2和Mg^2 时，有利于opal-A和坡缕石形成，当湖水具有低浓度溶解SiO2时，有利于opal-CT结晶。因此，沉淀SiO2的结构状态取决于地下水补给的湖水溶解SiO2浓度。富opal-A和富opal-CT交互层的形成是古气候、古水文周期性变化的指示。富opal-CT层指示高地下水补给流入量，低蒸发量，湖水低盐度和溶解组分，代表湿润气候时期；而富opal-A层代表低地下水补给流入量，高蒸发量，高溶解组分浓度，代表干旱气候时期。
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| 关 键 词： | 粘土 蛋白石 成因分析 地质背景 矿物学特征 |
| 文章编号： | 1000-4734(2005)01-081-08 |
| 修稿时间： | 2004年5月21日 |
CHARACTERISTICS AND SIGNIFICANCE OF OPALS IN PALYGORSKITE CLAY AT THE BOUNDARY BETWEEN JIANGSU AND ANHUI PROVINCES |
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| CHEN Tian-hu,XU Xiao-chun,XU Hui-fang,YUE Shu-cang.CHARACTERISTICS AND SIGNIFICANCE OF OPALS IN PALYGORSKITE CLAY AT THE BOUNDARY BETWEEN JIANGSU AND ANHUI PROVINCES[J].Acta Mineralogica Sinica,2005,25(1):81-88. |
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| Authors: | CHEN Tian-hu XU Xiao-chun XU Hui-fang YUE Shu-cang |
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| Institution: | CHEN Tian-hu~ |
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| Abstract: | TEM and XRD results showed that opals in the palygorskite opal layers of palygorskite clay deposits at the boundary between Anhui and Jiangsu Provinces are divided into opal-A and opal-CT. The palygorskite-opal layers consist of palygorskite, opal-A, opal-CT, a small amount of dolomite and other minerals. These layers show oscillation of opal-A-rich layer (OARLs) and opal-CT-rich layers (OCTRLs). The thickness of the layers may vary in a range of several centimeters. All these minerals are authigenic minerals that crystallized from solutions of evaporating lake. It is proposed that the components for the minerals (Si, Mg, Al) were supplied by shallow groundwater that is from surrounding basalt. OCTRLs indicate the periods of humid climate with a high input of groundwater and low evaporation that is low in soluble components. However, OARLs indicate the periods of dry climate with a low input of groundwater and high evaporation that contains high soluble components. The lake water with the high concentrations of soluble silica and other components favors the formation of opal-A and palygorskite. However, the lake water with the low concentrations of soluble silica and other components favors the crystallization of opal-CT with a small amount of palygorskite. So the formation of silica polymorphism is controlled by the concentrations of soluble silica in lake water that is derived mainly from groundwater. The oscillation of opal-A and opal-CT layers may be used as an indicator of odical changes of paleoclimate and paleohydrology. |
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| Keywords: | opal opal-CT palygorskite dolomite palaeoclimate paleohydrology sedimentation basalt |
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