Compositional variations, chemical weathering, and provenance of sands from the Cox’s Bazar and Kuakata beach areas, Bangladesh
Compositional variations, chemical weathering, and provenance of sands from the Cox’s Bazar and Kuakata beach areas, Bangladesh
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孟加拉国考克斯巴扎尔和夸卡塔海滩地区沙子的成分变化、化学风化和来源
DOI：
10.1007/s12517-018-4111-4
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发表时间：
2018
影响因子：
--
通讯作者：
Araoka Daisuke
中科院分区：
文献类型：
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作者：
Hossain H. M. Zakir;Hasna Hossain Quazi;Kamei Atsushi;Araoka Daisuke
对孟加拉国Cox 's Bazar海滩（CBB）和Kuakata海滩（KB）地区的沙子进行了模态和化学成分研究，以推断其成熟度、化学风化和物源特征。CBB和KB砂具有典型的高石英、低长石、岩屑等特征，为再造造山带源。CBB砂的主要元素组成具有高SiO2（83.52 ~ 89.84 wt%）和低Al2O3（4.39 ~ 6.39 wt%）的特征，而KB砂的SiO2含量相对较低（63.28 ~ 79.14 wt%）， Al2O3含量较高（9.00 ~ 11.33 wt%）。海滩砂的主量、微量元素和稀土元素（REE）组成相对于上大陆地壳（UCC）均表现出富集Th和sio2的特征，具有可比性。KB砂的Pb、Rb、Y和Fe略高于UCC，其余元素在两组中都被标为贫化，反映了河流搬运过程中斜长石和钾长石的破坏。CBB砂和KB砂在性质上属于低成熟至未成熟砂，分别属于亚粗砂岩和岩屑岩。CBB和KB砂岩的球粒陨石归一化稀土模式显示LREE富集，HREE接近平坦（LaN/YbN分别为7.64 ~ 9.38和5.48 ~ 8.82），且Eu/Eu*异常（Eu/Eu*分别为0.51 ~ 0.72和0.52 ~ 0.76），表明物源为长英质。物源鉴别图、固定微量元素比值（Th/Sc、Zr/Sc、Ce/Sc和Ti/Zr）和REE（∑LREE/HREE、Eu/Eu*和GdN/YbN）参数表明，CBB和KB砂岩主要来源于长英质烃源岩，其组成接近流纹岩、花岗闪长岩、花岗岩和UCC的平均值。
The modal and chemical composition of sands from Cox’s Bazar beach (CBB) and Kuakata beach (KB) areas of Bangladesh has been investigated to infer their maturity, chemical weathering, and provenance signatures. The CBB and KB sands are typically high quartz, low feldspar, and lithic fragments, representing a recycled orogen source. Major element compositions of CBB sands are characterized by high SiO2(83.52–89.84 wt%) and low Al2O3(4.39–6.39 wt%), whereas KB sands contained relatively low SiO2(63.28–79.14 wt%) and high Al2O3(9.00–11.33 wt%) contents. The major, trace and rare earth element (REE) compositions of beach sands display comparable distribution patterns with enriched Th and SiO2for both sands relative to upper continental crust (UCC). Pb, Rb, Y, and Fe for KB sands are little higher than UCC and the rest of the elements are marked depleted for both suites reflecting destruction of plagioclase and K-feldspar during fluvial transportation. The CBB and KB sands are compositionally low mature to immature in nature subsequently classified as subarkose and litharenite, respectively. Chondrite-normalized REE patterns for CBB and KB sands show LREE enrichment and nearly flat HREE (LaN/YbN, 7.64–9.38 and 5.48–8.82, respectively) coupled with prominent Eu anomalies (Eu/Eu*, 0.51–0.72 and 0.52–0.76, respectively), suggesting felsic source provenance. The provenance discrimination diagrams, immobile trace element ratios (Th/Sc, Zr/Sc, Ce/Sc, and Ti/Zr), and REE (∑LREE/HREE, Eu/Eu* and GdN/YbN) parameters indicate that CBB and KB sands were largely derived from felsic source rocks, with compositions close to average rhyolite, granodiorite, granite, and UCC.