Faculty of Geology, Geophysics and Environmental Protection, AGH University of Science and Technology, 30 Mickiewicza Av., 30-059, Kraków, Poland.
Polish Geological Institute-National Research Institute, Upper Silesian Branch, 1 Królowej Jadwigi Str., 41-200, Sosnowiec, Poland.
Sci Rep. 2021 Sep 17;11(1):18556. doi: 10.1038/s41598-021-96520-3.
The paper presents comprehensive mineralogical and geochemical characteristics of Dominican amber-bearing sediments from Siete Cañadas, Hato Mayor Province of the Eastern Mining District (EMD) in the Cordillera Oriental. The characteristics of rocks collected from the borehole in Siete Cañadas area (EMD) were compared with petrography of coaly shales from La Cumbre in the Northern Mining District (NMD). The mineralogy of the rocks was determined using transmitted and reflected light microscopy, scanning electron microscopy, Powder X-ray diffraction and Fourier Transform Raman Spectroscopy. Biomarker analyses by the gas chromatography-mass spectrometry were used to trace the genetic source and transformation stage of organic matter hosted in the core sediments. In this study, the characteristics of rocks from La Cumbre were supplemented with the petrographic data from our studies reported earlier. Based on the findings, it has been concluded that the basins in the investigated parts of the EMD and NMD regions were likely characterized by different, isolated palaeosettings. Transformation and maturation of terrigenous material were affected by locally occurring physicochemical conditions. In both amber deposits, the sedimentation of clastic and organic material proceeded in the presence of marine conditions. In case of the La Cumbre deposit (NMD area), the sedimentation underwent probably in the conditions of the lagoon environment, a shallow maritime lake or periodically flooded plain that facilitated organic matter decomposition and carbonation from meta-lignite to sub-bituminous coal (random reflectance of coal-R = 0.39%). In the Siete Cañadas (EMD region), the sedimentation took place in a shallow saltwater basin, where terrigenous material was likely mixed with material found in situ (fauna fossils, carbonate-group minerals) to form the mudstones enriched in bituminous substance of low maturity. The organic matter found in the rocks from both deposits is of mixed terrestrial/marine origin and was deposited in the presence of low oxygen concentration and reducing and/or dysoxic conditions.
本文介绍了多米尼加琥珀产地——东方山脉东部矿区（EMD）Siete Cañadas 地区含琥珀沉积物的综合矿物学和地球化学特征。对 Siete Cañadas 地区钻孔采集的岩石特征与北方矿区（NMD）La Cumbre 的煤系页岩岩相进行了比较。使用透射和反射光显微镜、扫描电子显微镜、粉末 X 射线衍射和傅里叶变换拉曼光谱法确定了岩石的矿物学。使用气相色谱-质谱法进行生物标志物分析，以追踪核心沉积物中有机质的遗传来源和转化阶段。在本研究中，La Cumbre 的岩石特征辅以我们之前研究报告的岩相数据。基于这些发现，可以得出结论，在所研究的 EMD 和 NMD 地区的盆地可能具有不同的、孤立的古环境。陆源物质的转化和成熟受局部物理化学条件的影响。在两个琥珀矿床中，碎屑和有机物质的沉积都是在海洋条件下进行的。在 La Cumbre 矿床（NMD 地区），沉积作用可能发生在泻湖环境、浅海湖泊或周期性洪水泛滥平原的条件下，有利于有机物质分解和从半腐殖煤到亚烟煤的碳化（煤的随机反射率-R=0.39%）。在 Siete Cañadas（EMD 地区），沉积作用发生在一个浅盐水盆地中，其中陆源物质可能与原地物质（动物化石、碳酸盐矿物群）混合，形成富含低成熟度沥青质的泥岩。两个矿床岩石中的有机质均具有陆地/海洋混合来源，在低氧浓度和还原/缺氧条件下沉积。
