泰国湾西部表层沉积物重矿物分布特征:对物质来源和沉积环境的指示

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对泰国湾西部159个表层沉积物进行了碎屑重矿物鉴定分析,其中57站重矿物颗粒数少于300粒,有效数据102站。结果表明,泰国湾西部表层沉积物中重矿物含量低,平均为1.628%,变化范围在0.016%~20.755%之间;共鉴定出重矿物29种,包括菱铁矿、褐铁矿、普通角闪石、自生黄铁矿、赤铁矿、绿帘石、磁铁矿、白钛石、锆石、紫苏辉石、石榴子石、黑云母、水黑云母、普通辉石、透闪石、白云母、钛铁矿、白云石、榍石、磷灰石、绢云母、蓝晶石、十字石、阳起石、电气石、金红石、棕闪石、独居石和透辉石,其中优势矿物为菱铁矿、普通角闪石和褐铁矿,平均含量(颗粒百分含量,下同)分别为41.6%,15.6%和13.4%,最高含量分别为99.7%,72%和94%;特征矿物为自生黄铁矿、磁铁矿、赤铁矿和锆石,平均含量分别为6.8%,4.1%,3.9%和0.9%,最高含量分别为97.3%,26.0%,91.7%和11.0%。利用数学聚类方法并结合矿物分布,在泰国湾西部划分出6个重矿物分区,基本以从北到南垂直岸线的东西向带状分布,矿物分区与物质来源和沉积环境具有较好的对应关系。重矿物来源主要为陆源和自生源:前者以普通角闪石、磁铁矿、赤铁矿、钛铁矿以及紫苏辉石等为代表性矿物,陆源物质输入较为明显的海区有3处,即曼谷湾的罗勇外部海区、春蓬和敦沙之间的近岸区域以及宋卡和北大年之间近岸区域,其中春蓬和敦沙之间的近岸区域表层沉积物中黑色金属矿物含量高,与附近有铁矿床分布相符合;后者以菱铁矿、自生黄铁矿以及菱铁矿风化形成的褐铁矿为代表性矿物,主要分布在陆架中南部、中东部和中北部。依据自生源矿物分布特征在陆架中部划分出不同的沉积环境,在陆架中南部和中北部为轻度还原环境,局部出现较强的还原环境,而在陆架中南部的轻度还原区域内出现氧化沉积环境。 A total of 159 surface sediments in the western Gulf of Thailand were analyzed for detrital heavy mineralization. Among them, the number of heavy minerals in 57 stations was less than 300, with 102 valid data. The results show that the heavy minerals in the surface sediments of the western Thailand Bay are low with an average of 1.628% and the variation ranges from 0.016% to 20.755%. A total of 29 heavy minerals are identified, including siderite, limonite, Amphibole, hematite, epidote, magnetite, white titanium stone, zircon, peridotite, garnet, biotite, water biotite, pyroxene, tremolite , Muscovite, ilmenite, dolomite, limonite, apatite, sericite, kyanite, plagioclase, actinolite, tourmaline, rutile, plagioclase, monazite and diopside, among which the predominant minerals Which are 41.6%, 15.6% and 13.4% respectively, with the highest contents of 99.7%, 72% and 94% respectively. The characteristic minerals They are 6.8%, 4.1%, 3.9% and 0.9% respectively, with the highest content of 97.3%, 26.0%, 91.7% and 11.0%, respectively, for the authigenic pyrite, magnetite, hematite and zircon. Using the method of mathematical clustering and mineral distribution, six heavy mineral subdivisions were divided in the western part of the Gulf of Thailand. The heavy mineral subdivisions basically distributed in an east-west direction from north to south vertical shoreline. Mineral subdivision and material source and sedimentary environment had good Corresponding relationship. The main sources of heavy minerals are terrestrial and authigenic: the former is represented by common hornblende, magnetite, hematite, ilmenite and peridotite as the representative minerals, the terrestrial input is more obvious in three sea areas, That is, the outer sea area of ​​Rayong in Bangkok Bay, the nearshore area between Chumphon and Dusha and the nearshore area between Songkhla and Pattani, of which the black metal mineral Which is consistent with the distribution of nearby iron deposits. The latter is characterized by siderite, limnetic pyrite and siderite formed of weathering of limonite as the representative minerals, mainly in the central and southern shelf, the middle and east North. According to the distribution characteristics of the spontaneous minerals, different sedimentary environments are divided in the middle part of the shelf. In the south and north-central parts of the shelf, there is a slight reduction environment, and a strong reduction environment appears locally. In the mild reduction area in the south of the shelf, oxidation occurs Sedimentary environment.
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