鄂尔多斯盆地东部本溪组铝土岩系的物质来源  

Provenance of the bauxite rock series in the Benxi Formation in the eastern Ordos Basin

作　　者：张雷[1,2] 王爱国[3,4] 潘博[1,2] 张海峰[5] 任懿炜 宁星辉 魏晋翔 王杰 ZHANG Lei;WANG Aiguo;PAN Bo;ZHANG Haifeng;REN Yiwei;NING Xinghui;WEI Jinxiang;WANG Jie(Research Institute of Exploration and Development,PetroChina Changqing Oilfield Company,Xi'an 710018,China;National Engineering Laboratory for Exploration and Development of Low Permeability Oil and Gas Fields,Xi'an 710018,China;Department of Geology,Northwest University,Xi’an 710069,China;State key Laboratory of Continental Dynamics,Northwest University,Xi’an 710069,China;Exploration Division of PetroChina Changqing Oilfield Company,Xi'an 710018,China)

机构地区：[1]中国石油长庆油田分公司勘探开发研究院,陕西西安710018 [2]低渗透油气田勘探开发国家工程实验室,陕西西安710018 [3]西北大学地质学系,陕西西安710069 [4]西北大学大陆动力学国家重点实验室,陕西西安710069 [5]中国石油长庆油田分公司勘探事业部,陕西西安710018

出　　处：《天然气地球科学》2024年第8期1351-1362,共12页Natural Gas Geoscience

基　　金：中国石油长庆油田分公司勘探开发研究院项目(编号:CQYT-CQKTY-2022-JS-2959)资助.

摘　　要：鄂尔多斯盆地铝土岩气勘探取得重大突破,然而铝土岩成因仍不清楚,其中一个关键问题是物质来源问题尚未解决。采用碎屑锆石年代学和稳定元素地球化学的方法对鄂尔多斯盆地东部神木—米脂地区本溪组铝土岩系开展了物质来源分析。结果显示:铝土岩系中的碎屑锆石为棱角状的岩浆锆石,粒径以0.03~0.06 mm为主,年龄峰值为500~400 Ma和350~300 Ma。铝土岩系上覆碎屑岩中的锆石主要为椭圆状变质成因锆石,粒径介于0.06~0.13 mm之间,约一半的锆石年龄是不谐和的,谐和年龄峰值为2600~2300 Ma和2100~1700 Ma。铝土岩系明显富集稳定元素,且与下伏碳酸盐岩具有相近的Zr/Nb值,但明显不同于上覆碎屑岩和盆内马家沟组凝灰岩的Zr/Nb值。对比分析后认为,盆地北部的华北板块基底是上覆碎屑岩的物源,但对铝土岩系的物质贡献较少。盆内下古生界和石炭纪凝灰岩是铝土岩系中碎屑锆石的直接来源,但它们对铝土岩系的物质贡献也极其有限。铝土岩系的主要物质来源为盆内下古生界碳酸盐岩。Significant breakthroughs have been made in the exploration of bauxite rock gas in the Ordos Basin,but the petrogenesis of bauxite rock is still unclear.One of the key issues is that the provenance of bauxite rock has not been resolved yet.Therefore,this study conducted provenance analysis on the bauxite rock series in the Benxi Formation in the Shenmu-Mizhi area of the eastern Ordos Basin using methods of detrital zircon chronology and stable element geochemistry.The results show that the detrital zircons in the bauxite rock series are angular shaped magmatic zircons,with particle sizes ranging from 0.06 mm to 0.03 mm.The zircon age displays two peaks,which correspond to 500-400 Ma and 350-300 Ma,respectively.The zircons in the overlying clastic rocks of the bauxite rock series are mainly elliptical metamorphic zircons with particle sizes ranging from 0.13 mm to 0.06 mm.About half of the zircon ages are disharmonious.The harmony age peaks of zircon are 2600-2300 Ma and 2100-1700 Ma.The bauxite rock series are significantly enriched in stable elements.Their Zr/Nb values are similar to those of the underlying carbonate rocks,but are significantly different from the Zr/Nb values from the overlying clastic rocks and the tuffs in the Majiagou Formation in the basin.After comparative analysis,it is believed that the North China Craton basement to the northern basin is the provenance of the overlying clastic rocks,but makes little material contribution to the bauxite rock series.The Lower Paleozoic and Carboniferous tuffs in the basin are the direct sources of detrital zircons in the bauxite rock series,but their material contribution to the bauxite rock series is extremely limited.The main provenance of the bauxite rock series is the Lower Paleozoic carbonate rocks within the Basin.

关 键 词：鄂尔多斯盆地 本溪组 铝土岩 铝土岩系 物源 神木地区 米脂地区 

分 类 号：TE121.1[石油与天然气工程—油气勘探]