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Facies analysis and depositional environment of Baluti Formation (Late Triassic) were studied from the Galley Derash section in the High Folded Zone and Sararu section in Northern Thrust Zone, from Duhok area, Kurdistan region, Northern Iraq. Lithologically, the Galley Derash section comprises 73 m brecciated dolomitic marly limestone, bedded dolomitic limestone, and brecciated sandy limestone which all interbedded with dark gray shale, while in Sararu section, it comprises 90 m of sandy dolomitic limestone interbedded with gray shale and brecciated marly limestone. Depending on field observations and petrographic analysis, three different litho units were recognized in the Baluti Formation in Galley Derash section and the same numbers of litho units were recognized in Sararu section with slight difference in lithology comparing to the Galley Derash. The petrographic study of the formation is based on 32 thin sections which showed that the majority of carbonates are carbonate mud (micrite) with less sparite. The skeletal grains include benthic foraminifera, dasycladacean algae, calcareous red algae, ostracods, brachiopods, bivalves, calcispheres, echinoderms, gastropods, ammonoids, and bioclasts. Non-skeletal grains involve peloids, extraclasts, intraclasts, and ooids. Based on detailed microfacies analysis of carbonate and field description, nineteen lithofacies types are distinguished in both studied sections of Baluti Formation. These facies were grouped relating to their environmental interpretation, into three basic types of facies associations: back shoal/lagoon, shoal, and foreshoal/slope. The field observation and petrographic, facies, and textural analysis indicate that Baluti Formation was deposited in the lower part of the lagoonal environment which changed into shoal and foreshoal/slope toward the upper part in the Galley Derash section, whereas in Sararu section, it was deposited under back shoal/lagoonal conditions including repeated intervals of shoal environment which changed into foreshoal/slope in the upper part.

Advanced techniques such as scanning electron microscope hot-cathodoluminescence (SEM-CL) and electron microprobe analysis (EMPA) as well as petrography are applied to investigate the paragenetic sequence and provenance of intertidal–tidal flat sandstones of the Ora Formation which is exposed in northern Iraq. The Formation consists mostly of supermature quartzarenites with subordinate immature subarkoses and sublitharenites. The mean framework composition of the thinly bedded sandstones of Ora Formation is Q95.7F2.8R1.4 where 90% of the quartz grains are monocrystalline and texturally supermature. Meanwhile the mean composition of the thickly bedded sandstones is Q85.4F9.7R4.8 with 84% of the quartz grains are monocrystalline and texturally immature. The provenance of the Ora sandstones is dominantly craton interior and less recycled orogeny. The Ora Formation has undergone intensive and complex episodes of eogenesis, mesogenesis, and telogenesis. Compaction and quartz cementation is more dominant than other diagenetic processes evident from tight grain supported fabric which predated authigenic illite formation; this is also evident from close packing of detrital framework that resulted in reduction of primary porosity. Albitization has postdated eogenesis of K-feldspar cements. Cathodoluminescence study indicated four main distinctive fabrics in quartz grains, (1) healed fractures, (2) mottled textures, (3) low-intensity dark CL streaks and patches, and (4) shocked quartz. The results indicate the dominance of brown to dark blue CL for quartz of low-temperature metamorphic origin; bright blue colors for the felsic plutonic and high-temperature metamorphic quartz; with considerable amounts of detritus that has originated from felsic and mafic volcanic rocks and are characterized by red, violet colors luminescence.

A combination of high resolution cathodoluminsecnce-spectroscopy (HRS-CL) with spatial electron microprobe analysis and optical microscopy is used to determine paragenesis and history of cementation in the limestones and dolostones of Khurmala Formation which is exposed in many parts of Northern Iraq. Khurmala Formation was subjected to different diagenetic processes such as micritization, compaction, dissolution, neomorphism, pyritization and cementation that occurred during marine to shallow burial stages and culminated during intermediate to deep burial later stages. Five dolomite textures are recognized and classified according to crystal size distribution and crystal-boundary shape. Dolomitization is closely associated with the development of secondary porosity that pre-and postdates dissolution and corrosion; meanwhile such porosity was not noticed in the associated limestones. Microprobe analysis revealed three types of cement, calcite, dolomite and ankerite which range in their luminescence from dull to bright. Cathodoluminescence study indicated four main texture generations. These are (1) unzoned microdolomite of planar and subhedral shape, with syntaxial rim cement of echinoderm that show dull to red luminescence, (2) equant calcite cements filling interparticle pores which shows dull luminescence and weak zonal growth, (3.1) homogenous intrinsic blue stoichiometric calcite with dull luminescence and without activators, (3.2) coarse blocky calcite cement with strong oscillatory zoning and bright orange luminescence which postdates other calcite cements, (4) ankerite cement with red to orange, non-luminescence growth zonation which is the last formed cement.

The Ordovician deltaic to shallow marine Khabour Formation in Northern Iraq consists mainly of sandstone with minor siltstone and interbedded shale. The sandstones are pervasively cemented by quartz that resulted in very little preserved primary porosity. Cathodoluminescence and petrographic studies showed that the silica cementation occurred in five successive phases which can be distinguished by their luminescence pattern. The precipitations of two phases have predated the major compaction process while the other phases are younger. The successive phases represent a sequence of changes in silica supply which were classified as very early and early, derived from dissolved biogenic silica that precipitated as opal/microquartz, possibly pre-compactional and of non-luminescent quartz overgrowth type. This was followed by phases whose silica supply derived from pressure solution of quartz, dissolution of feldspar, and hydrothermal fluids related to major thrust fault event. These successive quartz cement phases showed an increase in luminescence and the development of complicated zonation pattern in late-stage quartz cementation.

Outcrops of the Paleozoic Chalki volcanic rocks are restricted to part of the northern Thrust Zone of Iraq close to Iraqi-Turkish border. Petrographically, the volcanic rocks from the Chalki area are mainly layered, appearing fresh in the field and exhibiting some basaltic lava flows. Porphyritic, amygdaloidal, and microlite-porphyric are the main observed textures. Phenocrysts of primary phases (i.e., olivine, iron oxides) are in a groundmass of feldspars and clinopyroxene. Chalki Formation is intercalated with Pirispiki Formation which consists of thin to medium bedded, greenish gray marl, red mudstone, and veins of calcite. The Chalki rocks are mafic of theolitic basalt type. Geochemically, they have high chromium and nickel concentrations in most samples. Rare earth element (REE) patterns illustrate parallel to sub-parallel, moderately fractionated REE patterns. The low heavy REE (HREE) contents in the studied samples appear to be due to partial melting of metamorphosed oceanic crust leaving HREE-rich accessory minerals (i.e., garnet) as a residual phase in the source. No Eu anomalies were observed in the Chalki samples which may indicate a back-arc basin pattern. The non-subduction signature of the Chalki rocks is confirmed by the Nb/Yb versus Th/Yb diagram, which shows that most of the studied rocks fall in the compositional field of non-arc-related rocks—well within the field of the mid-ocean ridge basalt (MORB)-ocean island basalt (OIB) mantle array.