【摘要】：研究區(qū)位于內(nèi)蒙古自治區(qū)阿拉善盟阿拉善右旗。區(qū)內(nèi)古生界以恩格爾烏蘇縫合帶為界,分為西北部的塔里木-南疆大區(qū)和東南部的華北地層大區(qū),上古生界的上石炭統(tǒng)本巴圖組(C2bb)位于華北地層大區(qū),主要出露于恩格爾烏蘇-東德烏蘇-撒拉-查干楚布一帶。根據(jù)巖石組合特征,將研究區(qū)本巴圖組自下向上分為三段:一段以中厚層大理巖(原巖為灰?guī)r)為主,夾有變質(zhì)中細(xì)粒含鈣質(zhì)巖屑砂巖和變質(zhì)粉細(xì)砂巖,為淺海碳酸巖臺地沉積;二段為變質(zhì)礫巖、變質(zhì)含鈣質(zhì)粉細(xì)砂巖和大理巖,礫巖多呈透鏡狀發(fā)育,變質(zhì)含鈣質(zhì)粉細(xì)砂巖呈薄層狀發(fā)育,為半深海斜坡沉積;三段包括變質(zhì)砂巖和千枚巖,部分層位變質(zhì)砂巖中可見黃鐵礦晶體和鮑馬序列,反映深水還原環(huán)境,為深海-半深海濁積扇沉積。根據(jù)在恩格爾烏蘇本巴圖組剖面(PM122)上采集的本巴圖組變質(zhì)砂巖和侵入其中巖脈的樣品進(jìn)行鋯石年齡測定。本巴圖組變質(zhì)砂巖中碎屑鋯石的最小年齡407±3Ma和侵入本巴圖組中的巖脈的巖漿鋯石的最大年齡267±3Ma,結(jié)合鄰區(qū)古生物資料大致確定本巴圖組時代應(yīng)為晚石炭世。研究區(qū)本巴圖組三段砂巖化學(xué)成分中Si O2含量變化較大,在42.96%-78.41%之間變化,平均61.74%。變質(zhì)砂巖中Al2O3含量較高(7.52%-16.95%),平均含量為13.34%。本巴圖組砂巖的化學(xué)蝕變指數(shù)(CIA)較高,介于58.66-76.4之間,平均值為65.82,表明沉積物源區(qū)的風(fēng)化作用較為強(qiáng)烈或者經(jīng)歷了沉積物再循環(huán)作用。利用(Fe2O3t+Mg O)-Ti O2圖解和(Fe2O3t+Mg O)-Al2O3/(Ca O+Na2O)圖解進(jìn)行判別,表明本巴圖組三段的形成環(huán)境與活動構(gòu)造背景相關(guān)。稀土元素分析結(jié)果顯示:樣品均為輕稀土元素富集型,Eu呈現(xiàn)負(fù)異常。樣品∑REE值較大,平均為平均為143.85×10-6,反映與島弧相關(guān)的特征。綜合巖性組合特征、沉積構(gòu)造和地球化學(xué)分析可知:本巴圖組一段沉積環(huán)境為穩(wěn)定背景下的淺海碳酸鹽臺地;二段沉積環(huán)境為過渡帶,此段代表了大地構(gòu)造背景由穩(wěn)定到活動的轉(zhuǎn)換;三段沉積環(huán)境為活動背景下的深�！肷詈！�
[Abstract]:The research area is located in the right flag of Alashan League of Inner Mongolia Autonomous region. The Paleozoic is divided into the Tarim and South Xinjiang regions in the northwest and the North China stratigraphic region in the southeast, and the Upper Carboniferous Ben-Gbatu formation (C2bb) in the Upper Paleozoic is located in the North China stratigraphic region. Mainly exposed in the Engloussu-East Germany Usu-Sara-Chaganchub area. According to the characteristics of rock assemblage, the BenGbatu formation in the study area is divided into three sections from the bottom up: the first section is composed of medium and thick marble (primary limestone), intercalated with metamorphic fine-grained calcareous lithic sandstone and metamorphic silty sand. It is a shallow carbonate platform deposit; The second stage is metamorphic conglomerate, metamorphic calcareous silty sand and marble, the conglomerate is mostly lenticular, metamorphic calcareous silty sand is thin layer, it is semi-deep sea slope deposit. The three formations include metamorphic sandstone and phyllite, and pyrite crystals and Baoma sequences can be found in some of the metamorphic sandstone, reflecting the deep-water reduction environment and the deep-sea and semi-deep-sea turbidite fan deposits. Zircon dating was performed on the metamorphic sandstone and intrusive veins of the Ben Gbatu formation collected from the PM122 section of the Englesu Ben Gbatu formation. The minimum age of detrital zircon in metamorphic sandstone of the Ben Gbatu formation is 407 鹵3Ma and the maximum age of magmatic zircon intruding into the vein of the Ben Gbatu formation is 267 鹵3 Ma. combined with the paleontological data of the adjacent area, it is generally determined that the age of the Ben Gbatu formation should be the late Carboniferous. The content of Si O 2 in the chemical composition of sandstone of the third member of the Benjiao formation in the study area varies greatly, ranging from 42.96% to 78.41%, with an average of 61.74%. The content of Al2O3 in metamorphic sandstone is higher (7.52% -16.95%), and the average content is 13.34%. The chemical alteration index (CIA) of the sandstone of the Gbatu formation is higher, ranging from 58.66 to 76.4, with an average value of 65.82, which indicates that the weathering in the source area of the sediments is relatively strong or has experienced sediment recirculation. The (Fe2O3t Mg O) Ti O 2 diagram) and (Fe2O3t Mg O) Al2O3/ (Ca O Na2O) diagram are used to distinguish the formation environment of the third member of the Gbatu formation is related to the active tectonic background. The results of REE analysis showed that all samples were light REE enriched type and Eu showed negative anomaly. The mean 鈭，

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