The Tabas Basin is in the Tabas Block in the central part of Iran, and it contains Iran’s largest coal deposits, mostly in the Parvadeh Coalfield. The basin is structurally characterised by regional scale thrust faults and orthogonal strike-slip faults that segregate the coalfields into different areas namely Parvadeh (P) I to IV. The coals under study are in the upper Triassic Nayband Formation. Samples were collected from underground coal mines in PI, PII, PIII, and core from PIV, and prepared for petrographic analysis. The resulting vitrinite reflectance varies between 1.13% and 1.54%, which places the coals into medium volatile bituminous rank. In all samples, the vitrinite content is significantly higher than the inertinite followed by minor amounts of liptinite, mostly secondary exsudatinite. The samples also contain abundant pseudovitrinite, which can be above 40% (volume, mineral matter free basis). The maceral composition and moderate to high mineral matter with common framboidal pyrite and siderite corroborate previous interpretations of the Parvadeh coals forming in topogenous to transitional peatlands in paralic to fluvial palaeoenvironments. However, this study makes additional interpretations of the coalification history of the Parvadeh coals and the occurrence of pseudovitrinite. The coals commonly contain meta-cutinite and associated meta-exsudatinite, and fluorescing exsudatinite that permeates carbargillite lenses, lumina of inertinite macerals, and the slits of the pseudovitrinite. This suggests at least two stages of hydrocarbon generation occurred in the Parvadeh coals: the first phase during entry into the oil window and later devolatilisation to meta- exsudatinite in the early gas window; the second phase post-dates this and could be generated internally from the vitrinite else migrated from surrounding organic-rich rocks in the interburdens of the Nayband Formation. The fact that the pseudovitrinite slits are filled with exsudatinite but not meta-exsudatinite indicates that pseudovitrinite formed just before during partial devolatilisation or contemporaneous with the second generation of exsudatinite. Epigenetic mineralisation includes massive pyrite and dolomite in the fractures, indicative of potential hydrothermal circulation that may also be related to the second phase of hydrocarbon generation as exsudatinite is found trapped in the intracrystalline spaces of the carbonates.

塔巴斯盆地位于伊朗中部的塔巴斯区块，蕴藏着伊朗最大的煤炭矿床，主要位于帕尔瓦德煤田。该盆地的结构特征是区域规模的逆冲断层和正交走滑断层将煤田分隔成不同的区域，即 Parvadeh (P) I 至 IV。研究中的煤位于上三叠统 Nayband 组。从 PI、PII、PIII 的地下煤矿和 PIV 的岩心采集样品，并准备用于岩相分析。由此产生的镜质体反射率在 1.13% 和 1.54% 之间变化，这将煤置于中等挥发性沥青等级。在所有样品中，镜质体含量显着高于惰性体，其次是少量的辉光体，主要是次生渗出体。样品还含有丰富的假镜质体，可高于 40%（体积，不含矿物质）。矿物成分和中度至高矿物质含量以及常见的棱柱状黄铁矿和菱铁矿证实了先前对 Parvadeh 煤形成于近河流古环境中的土生至过渡泥炭地的解释。然而，这项研究对 Parvadeh 煤的成煤历史和假镜质体的出现做出了额外的解释。煤通常含有间角硬质体和相关的间渗出晶岩，以及渗入卡巴吉石透镜、惰性显微体的腔和假镜质体的狭缝的荧光渗出晶岩。这表明在 Parvadeh 煤层中至少发生了两个碳氢化合物生成阶段：进入油窗的第一阶段，随后在早期的气窗脱挥发成偏渗出岩；第二阶段在此之后发生，可能是内部产生的镜质体，也可能是从 Nayband 组间岩层中周围富含有机物的岩石迁移而来。假镜质体狭缝中充满了渗出晶岩而不是偏渗出晶岩，这表明伪晶质体是在部分脱挥发分之前形成的，或者与第二代渗出晶岩同时形成。表观成矿包括裂缝中的块状黄铁矿和白云石，表明潜在的热液循环也可能与烃生成的第二阶段有关，因为在碳酸盐的晶内空间中发现了渗出岩。第二阶段在此之后发生，可能是内部产生的镜质体，也可能是从 Nayband 组间岩层中周围富含有机物的岩石迁移而来。假镜质体狭缝中充满了渗出晶岩而不是偏渗出晶岩，这表明伪晶质体是在部分脱挥发分之前形成的，或者与第二代渗出晶岩同时形成。表观成矿包括裂缝中的块状黄铁矿和白云石，表明潜在的热液循环也可能与烃生成的第二阶段有关，因为在碳酸盐的晶内空间中发现了渗出岩。第二阶段在此之后发生，可能是内部产生的镜质体，也可能是从 Nayband 组间岩层中周围富含有机物的岩石迁移而来。假镜质体狭缝中充满了渗出晶岩而不是偏渗出晶岩，这表明伪晶质体是在部分脱挥发分之前形成的，或者与第二代渗出晶岩同时形成。表观成矿包括裂缝中的块状黄铁矿和白云石，表明潜在的热液循环也可能与烃生成的第二阶段有关，因为在碳酸盐的晶内空间中发现了渗出岩。