The Thrace Basin hosts the second-largest natural gas and oil resource of Turkey. Several mineable late Oligocene coal seams are located close to natural gas fields in the basin. This study focuses on the assessment of late Oligocene seams in the Malkara coal field using mineralogical, petrographic, and Rock-Eval pyrolysis data. The variations in coal properties seem to be mainly controlled by common peat-forming vegetation and detrital input ratio into palaeomires. The studied samples are characterized by variable TOC, T_max and HI values and high H contents. Even though the relatively high H contents seem to be related to high total liptinite contents, the presence of hydrogen-rich telohuminite macerals, particularly ulminite A, may be the main reason for elevated H contents in the studied samples. Furthermore, the Rock-Eval analyses results, which imply the presence of mixed type III-IV kerogens, conflict with coal petrography data. The differences could be a by-product of carbonate minerals breakdown during pyrolysis; however; the presence of hydrogen-rich telohuminite macerals, which could have originated from resinous woody peat-forming plants, could cause suppression S₂ peak and elevation of S₃ peak due to release additional CO_x from the breakdown of hydrogen- and oxygen-rich compounds in telohuminite macerals during pyrolysis. Therefore, HI, T_max, and OI values are not matched with maceral compositions. Moreover, the relatively higher T_max and %Rr values of studied late Oligocene coal seams in the Malkara coal field than early Oligocene shales and late Oligocene coals in the NE parts of the basin could be related to higher thermal gradient and/or post-Oligocene tectonic movements. Overall, the results imply that the coals are mostly gas-prone; thus, the studied coal seams along with unexploited coal seams near to the study area have a hydrocarbon generation potential for especially natural gas in the Danişmen Formation. The results of this study also show that the Rock-Eval pyrolysis data of low-rank humic coals similar to Malkara coals should be used with caution and cross-checked with results of traditional coal parameters such as ash yields, H contents, maceral, and mineralogical compositions to avoid misinterpretations.

色雷斯盆地拥有土耳其第二大天然气和石油资源。几个可开采的晚渐新世煤层靠近盆地的天然气田。本研究的重点是使用矿物学、岩相学和 Rock-Eval 热解数据评估 Malkara 煤田晚渐新世煤层。煤特性的变化似乎主要受常见的泥炭形成植被和进入古煤的碎屑输入比例控制。研究样品的特征是可变的 TOC、T _max和 HI 值和高 H 含量。尽管相对较高的 H 含量似乎与高总 liptinite 含量有关，但富含氢的长辉石微晶的存在，尤其是 ulminite A，可能是研究样品中 H 含量升高的主要原因。此外，Rock-Eval 分析结果表明存在混合型 III-IV 干酪根，与煤岩相数据相冲突。这些差异可能是热解过程中碳酸盐矿物分解的副产品；然而; 由于释放额外的 CO _x，可能源自树脂木本泥炭植物的富含氢的长辉石微晶的存在可能导致 S ₂峰的抑制和 S ₃峰的升高来自热解过程中微辉石微晶中富含氢和氧的化合物的分解。因此，HI、T _max和OI 值与微晶成分不匹配。此外，相对较高的 T _max与盆地东北部早渐新世页岩和晚渐新世煤相比，Malkara 煤田中研究的晚渐新世煤层和 %Rr 值可能与较高的温度梯度和/或后渐新世构造运动有关。总体而言，结果表明煤大多是气体倾向的；因此，研究的煤层以及研究区附近未开发的煤层具有生烃潜力，尤其是在 Danişmen 组天然气。本研究的结果还表明，应谨慎使用类似于 Malkara 煤的低阶腐殖煤的 Rock-Eval 热解数据，并与传统煤参数（如灰分产量、H 含量、微分和矿物成分以避免误解。