(1. 中南大學(xué) 地球科學(xué)與信息物理學(xué)院，有色金屬成礦預(yù)測與地質(zhì)環(huán)境監(jiān)測教育部重點實驗室，長沙 410083；
2. 湖南省煤炭地質(zhì)勘查院，長沙 410019)
摘 要: 廣西平果鋁礦集區(qū)是我國重要的鋁土礦產(chǎn)地，有巖溶堆積型和原生沉積型兩種鋁土礦類型。前人主要專注于堆積型鋁土礦的成因研究，而對于原生礦的沉積相、古地貌、沉積環(huán)境及其對鋁土礦礦層的控制作用尚未開展具體分析。本文對礦區(qū)多種原生礦石開展了精細(xì)的礦物學(xué)及地球化學(xué)研究，結(jié)果表明：平果原生鋁土礦總體富集Zr、Ga、Th、U、V，虧損Sr、Ba；87Sr/86Sr值普遍較高，大多為0.7080~0.7085；原生礦中的鮞粒能譜掃描電鏡及電子探針分析顯示，不同樣品具有差異較大的O、Al、Si、Fe、K、Ti以及Ga元素含量。結(jié)合礦體野外產(chǎn)狀及空間分布特征，本文提出平果礦集區(qū)古地貌特征為東部、北部地勢較高，南部、西部地勢逐漸變低，從太平礦區(qū)到那豆礦區(qū)再到新安礦區(qū)，沉積環(huán)境呈現(xiàn)出近陸到遠(yuǎn)陸、水淺到水深的沉積環(huán)境變化，總體表現(xiàn)為海陸交匯沉積環(huán)境格局。原生鋁土礦成礦物質(zhì)依次被搬運(yùn)至太平礦區(qū)、那豆礦區(qū)和新安礦區(qū)沉積成礦，總體沉積環(huán)境為三角洲相；礦區(qū)三角洲沉積環(huán)境可進(jìn)一步分為分支河流相、沼澤相、沙壩相等沉積微相，其中，沙壩微相最有利于原生礦富集，因此平果礦集區(qū)的那榮地區(qū)和塘琴地區(qū)最有利于原生礦的形成。
關(guān)鍵字: 原生鋁土礦；沉積鮞粒；沉積相；成礦環(huán)境；廣西平果
（1. Key Laboratory of Metallogenic Prediction of Nonferrous Metals and Geological Environment Monitoring of Ministry of Education, School of Geosciences and Info？Physics, Central South University, Changsha 410083, China;
2. The Coal Geological Exploration Institute of Hunan Province, Changsha 410083, China）
Abstract:The Pingguo bauxite mining area in Guangxi is an important bauxite producing area in China. There are two types of bauxite ores: Karst accumulation type and primary sedimentation type. Previous researches mainly focused on the genesis of accumulative bauxite, but no specific analysis has been carried out on the sedimentary facies, paleogeomorphology, sedimentary environment and its control on the formation of primary sedimentation type ore. In this paper, detailed mineralogical and geochemical studies have been carried out on a variety of primary ores in the Pingguo area. The results show that the primary bauxite ore is generally enriched in Zr, Ga, Th, U and V but depleted in Sr and Ba. The 87Sr/86Sr values are generally high, mostly between 0.7080 and 0.7085. Energy spectrum scanning electron microscope and electron probe microanalysis of oolites in primary ore show that different samples have variable contents of O, Al, Si, Fe, K, Ti and Ga. Combined with the field occurrences and spatial location of the ore bodies, this study puts forward that the paleogeomorphic characteristics of the Pingguo mining area are that the terrain in the east and north is higher, whereas the terrain in the south and west is lower. The sedimentary environment from the Taiping area to Nadou area and then to Xin''''an area in Pingguo changed from near-land to far-land, and from shallow-water to deep-water, presenting the pattern of sea-land intersection sedimentary environment. The primary bauxite ore-forming materials were transported and deposited from Taiping to Nadou and then to Xin''''an. On the whole, it was a delta sedimentary environment which can be divided into more detailed sedimentary microfacies such as branch fluvial facies, swamp facies and sandbank facies. It is pointed out that sandbank microfacies were most conducive to the enrichment of primary ore. Therefore, the Narong and Tangqin areas in Pingguo were most conducive to the deposition of primary ore.
Key words: primary bauxite ore; sedimentary oolitic; sedimentary facies; metallogenic environment; Pingguo-Guangxi
