Regional sandstone-type uranium mineralization rooted in Oligo–Miocene tectonic inversion in the Songliao Basin,NE China

The tectonic inversion of the Songliao Basin during the Oligo–Miocene may have played an important role in controlling the development of sandstone-type uranium deposits (SUDs). Here we investigate drill holes along a southeast to northwest section in this basin based on apatite fission-track (AFT) and zircon fission-track (ZFT) techniques. We present 50 data from 15 deep boreholes at different depths between 665 and 3956 m and different structural units including grabens and horsts formed in the Early Cretaceous beneath the basin. The results of the effective AFT ages are 100 ± 11 to 2.3 ± 0.4 Ma (P(x²) > 5%) and ZFT ages are 97.5–20.4 Ma (including binomial peak ages). These results reveal that the basin underwent two distinct stages of rapid cooling after Late Cretaceous. In the first stage, during the Late Cretaceous–Early Paleogene (~80–50 Ma), tectonic uplift occurred in all of the structural units including grabens and horsts, which was marked by an unconformity between the latest Cretaceous Mingshui and the Eocene Yi'an formations. In the second stage, during the Oligo–Miocene (~40–10 Ma), tectonic uplift occurred mainly in the grabens but not in the horsts, corresponding with a few sediments of the Neogene Da'an and Taikang formations. We propose that the folds and the thrust faults mostly characterize in the second stage indicating a major tectonic inversion in the basin. The shifting of the two stages was probably in response to differences in the subduction angles and directions of motion of the Paleo-Pacific Plate from the southeast. Combined with previous information, it was demonstrated that most of the U mineralization ages are younger than 40 Ma, with a peak in the Miocene or later (<20 Ma). We thus propose that the SUDs have been redistributed and redeposited locally in successive stages during and after the Oligo–Miocene tectonic inversion.     

Hydrocarbon migration in the Zagros Basin,offshore Iran,for understanding the fluid flow in the Oligocene–Miocene carbonate reservoirs

Kuh-e Mond Field is a conventional heavy oil resource in the Zagros foreland Basin, Iran, produced from the fractured carbonates partially filled by dolomite, calcite, and anhydrite cement. Vitrinite reflectance data from carbonate reservoir suggest low-maturation levels corresponding to paleotemperatures as low as 50 °C. The observed maturation level (< 0.5% Rmax) does not exceed values for simple burial maturation based on the estimated burial history. Oil inclusions within fracture-filled calcite and dolomite cement indicate the key role of these fractures in oil migration.The fluid inclusion temperature profiles constructed from the available data revealed the occurrence of petroleum in dolomite, calcite, and anhydrite and characterize the distinct variations in the homogenization temperatures (T_h). Fluid inclusions in syntectonic calcite veins homogenize between 22 °C and 90 °C, showing a salinity decrease from 22 to 18 eq. wt.% NaCl. Fluid inclusions in anhydrite homogenize at < 50 °C, showing that the pore fluids became warmer and more saline during burial. The T_h range in the calcite-dolomite cement depicts a change in water composition; therefore, we infer these cements precipitated from petroleum-derived fluids. The microthermometry data on the petroleum fluid inclusions suggest that the reservoir was filled with heavy black oils and high-salinity waters and indicate that undersaturated oil was present in a hydrostatically pressured reservoir.The T_h data do not support vertical migration of hot fluids througout the section, but extensive lateral fluid migration, most likely, drove tectonically dewatering in the south or west of the pool.     

Facies analysis and depositional environments of the Oligocene–Miocene Asmari Formation, Zagros Basin, Iran

The Asmari Formation(a giant hydrocarbon reservoir)is a thick carbonate sequence of the Oligocenee Miocene in the Zagros Basin,southwest of Iran.This formation is exposed at Tang-e-Lendeh in the Fars interior zone with a thickness of 190 m comprising medium and thick to massive bedded carbonates.The age of the Asmari Formation in the study area is the late Oligocene(Chattian)eearly Miocene(Burdigalian).Ten microfacies are defned,characterizing a gradual shallowing upward trend;the related environments are as follows:open marine(MF 8e10),restricted lagoon(MF 6e7),shoal(MF 3e5),lagoon(MF 2),and tidal fat(MF 1).Based on the environmental interpretations,a homoclinal ramp consisting of inner and middle parts prevails.MF 3e7 are characterized by the occurrence of large and small porcelaneous benthic foraminifera representing a shallow-water setting of an inner ramp,infuenced by wave and tidal processes.MF 8e10,with large particles of coral and algae,represent a deeper fair weather wave base of a middle ramp setting.     

Plant–Arthropod Associations from the Lower Miocene of the Most Basin in Northern Bohemia (Czech Republic): A Preliminary Report

Terrestrial plants and insects currently account for the majority of the Earth's biodiversity, and approximately half of insect species are herbivores. Thus, insects and plants share ancient associations that date back more than 400 Myr. However, investigations of their past interactions are at the preliminary stages in Western Europe. Herein, we present the first results of our study of various feeding damage based on a dataset of nearly 3500 examined plant specimens from the Lower Miocene of the Lagerst?tte Bílina Mine in the Most Basin, Czech Republic. This site provides a unique view of the Neogene freshwater ecosystems. It has long been studied by scientists working in different branches of sedimentology, paleobotany, and paleozoology. The fossils are preserved in three characteristic horizons overlaying the coal seam (Clayey Superseam Horizon, Delta Sandy Horizon, and Lake Clayey Horizon), reflecting paleoenvironmental changes in a short time period of development. The trace fossils are classified as functional feeding groups or “guilds”, without searching for a direct cause or a recent analog host relation. Approximately 23% of specimens of dicotyledonous plant leaves were found to be damaged and associated with some leaf “morphotypes”. Deciduous plant–host taxa, and those with a chartaceous texture typical of riparian habitats, were frequently damaged, such as Populus, recorded with two species Populus zaddachii and Populus populina (57.9% and 31% herbivory levels, respectively), followed by Acer, Alnus, and Carya, averaging almost 30% of damaged leaves/leaflets. There has been evidence of 60 damage types (DT) representing all functional feeding groups recorded at the Bílina Mine, including 12 types of leaf mines and 16 gall-type DT. In total, Lower Miocene of the Lagerst?tte Bílina Mine exhibits a high level of external foliage feeding types (23.7%), and a low level of more specialized DT, such as galls (4.3%) and leaf mines (<1%). A broader comparison based on DT of the main sedimentary environments shows significance supporting different biomes by frequency of damage levels and DT diversities.     

Evolution and Application of Sealing Ability of Gypsum Caprocks under Temperature-Pressure Coupling: An Example of the ZS5 Well in the Tazhong Area of the Tarim Basin

Gypsum caprocks'' sealing ability is affected by temperature-pressure coupling. Due to the limitations of experimental conditions, there is still a lack of triaxial stress-strain experiments that simultaneously consider changes in temperature and pressure conditions, which limits the accuracy of the comprehensive evaluation of the brittle plastic evolution and sealing ability of gypsum rocks using temperature pressure coupling. Triaxial stress-strain tests were utilized to investigate the differences in the evolution of the confinement capacity of gypsum rocks under coupled temperature-pressure action and isothermal-variable pressure action on the basis of sample feasibility analysis. According to research, the gypsum rock''s peak and residual strengths decrease under simultaneous increases in temperature and pressure over isothermal pressurization experimental conditions, and it becomes more ductile. This reduces the amount of time it takes for the rock to transition from brittle to plastic. When temperature is taken into account, both the brittle–plastic transformation''s depth limit and the lithological transformation of gypsum rocks become shallower, and the evolution of gypsum rocks under variable temperature and pressure conditions is more complicated than that under isothermal pressurization. The sealing ability under the temperature-pressure coupling is more in line with the actual geological context when the application results of the Well #ZS5 are compared. This provides a theoretical basis for precisely determining the process of hydrocarbon accumulation and explains why the early hydrocarbon were not well preserved.     

Tectono–sedimentary Evolution of the Late Triassic Xujiahe Formation in the Sichuan Basin

The early stage of Sichuan Basin formation was controlled by the convergence of three major Chinese continental blocks during the Indosinian orogeny that include South China,North China,and Qiangtang blocks.Although the Late Triassic Xujiahe Formation is assumed to represent the commencement of continental deposition in the Sichuan Basin,little research is available on the details of this particular stratum.Sequence stratigraphic analysis reveals that the Xujiahe Formation comprises four third-order depositional sequences.Moreover,two tectono-sedimentary evolution stages,deposition and denudation,have been identified.Typical wedge-shaped geometry revealed in a cross section of the southern Sichuan Basin normal to the Longmen Shan fold-thrust belt is displayed for the entire Xujiahe Formation.The depositional extent did not cover the Luzhou paleohigh during the LST1 to LST2 （LST,TST and HST mean Iowstand,transgressive and highstand systems tracts,1,2,3 and 4 represent depositional sequence 1,2,3 and 4）,deltaic and fluvial systems fed sediments from the Longmen Shan belt,Luzhou paleohigh,Hannan dome,and Daba Shan paleohigh into a foreland basin with a centrally located lake.The forebulge of the western Sichuan foreland basin was located southeast of the Luzhou paleohigh after LST2.According to the principle of nonmarine sequence stratigraphy and the lithology of the Xujiahe Formation,four thrusting events in the Longmen Shan fold-thrust belt were distinguished,corresponding to the basal boundaries of sequences 1,2,3,and 4.The northern Sichuan Basin was tilted after the deposition of sequence 3,inducing intensive erosion of sequences 3 and 4,and formation of wedge-shaped deposition geometry in sequence 4 from south to north.The tilting probably resulted from small-scale subduction and exhumation of the western South China block during the South and North China block collision.     

Miocene Tectonic Evolution from Dextral-Slip Thrusting to Extension in the Nyainqentanglha Region of the Tibetan Plateau

Dextral-slip in the Nyainqentangiha region of Tibet resulted in oblique underthrusting and granite generation in the Early to Middle Miocene, but by the end of the epoch uplift and extensional faulting dominated. The east-west dextral-slip Gangdise fault system merges eastward into the northeast-trending, southeast-dipping Nyainqentangiha thrust system that swings eastward farther north into the dextral-slip North Damxung shear zone and Jiali faults. These faults were took shape by the Early Miocene, and the large Nyainqentangiha granitic batholith formed along the thrust system in 18.3-11.0 Ma as the western block drove under the eastern one. The dextral-slip movement ended at -11 Ma and the batholith rose, as marked by gravitational shearing at 8.6-8.3 Ma, and a new fault system developed. Northwest-trending dextral-slip faults formed to the northwest of the raisen batholith, whereas the northeast-trending South Damxung thrust faults with some sinistral-slip formed to the southeast. The latter are replaced farther to the east by the west-northwest-trending Lhunzhub thrust faults with dextral-slip. This relatively local uplift that left adjacent Eocene and Miocene deposits preserved was followed by a regional uplift and the initiation of a system of generally north-south grabens in the Late Miocene at -6.5 Ma. The regional uplift of the southern Tibetan Plateau thus appears to have occurred between 8.3 Ma and 6.5 Ma. The Gulu, Damxung-Yangbajain and Angan graben systems that pass east of the Nyainqentangiha Mountains are locally controlled by the earlier northeast-trending faults. These grabens dominate the subsequent tectonic movement and are still very active as northwest-trending dextral-slip faults northwest of the mountains. The Miocene is a time of great tectonic change that ushered in the modern tectonic regime.     

Metallogenic Model of Bauxite in Central Guizhou Province: an Example of Lindai Deposit

The bauxites in central Guizhou are hosted by the Lower Carboniferous Jiujialu Formation.Geochemistrial characteristics of the Lindai bauxite deposit indicate that the underlying Shilengshui Formation dolomite is the precursor rock of mineral resources.Weathering simulation experiments show that Si is most likely to migrate with groundwater,the migration rate of which is several magnitude higher than Al and Fe under nature conditions （pH=3-9）.The neutral and acid nonreducing condition is the most conducive to the Al rich and Si removal,while the acid reducing conditions is the most conducive to the Al rich and Fe removal.In the process of bauxite formation,coal beds overlying the Al-bearing rock series or other rock formation rich in organic materials can produce acid reducing groundwater,which are important for the bauxite formation.Finally,propose the metallogenic model of the bauxite in central Guizhou Province and put forward three new words which are ＂original bauxite material＂,＂bauxite material＂ and ＂original bauxite＂.     

Evolution of Stromatoporoidea in the Ordovician–Silurian epicontinental basin of the Siberian Platform and Taimyr

The paper discusses the evolution of Stromatoporoidea in the epicontinental sedimentary basin of the Siberian Platform and Taimyr during the Ordovician and Silurian. Specimens of the oldest genus, Priscastroma, were found in the middle of Middle Ordovician sediments. This genus is represented by the species P. gemina Khrom., which has two forms, A and B. Tracing the emergence of new genera over time, we identified two distinct branches in stromatoporoid evolution.The ancestor of the first branch is P. gemina f. A, which gave rise to the genus Cystostroma. The latter is the ancestor of two subbranches with predominant horizontal skeletal elements. The subbranches differ only in tissue microstructure. The genera Stromatocerium, Dermatostroma, and Aulacera display dense fibrous microstructure, whereas the genus Rosenella and its descendants display dense microstructure. The genus Lophiostroma, with a lamellar–fibrous tissue, may be a dead branch of evolution.The ancestor of the second branch is P. gemina f. B, which gave rise to the genus Labechia and its descendants. This branch has a dense tissue, with predominant vertical skeletal elements.Ordovician stromatoporoids from Siberia were compared with those from other basins of the world. Comparison shows that all the Ordovician genera from the epicontinental basin of the Siberian Platform and Taimyr originated here. Thus, this basin was one of the centers of stromatoporoid origin.     

Tectonic Evolution and Petroleum Systems in the Junggar Basin

The Junggar basin is located in the northern part of Xinjiang of China. It is part of the Kazakstan plate, surrounded by the Paleozoic folded mountains: the Halaart, Zayier and Chepaizi Mountains in the northwest, the Qingelidi and Karamaili Mountains in the northeast, and the Tianshan Mountains in the south. In different evolution stages, the basin's types are different, and the stratigraphy and deposition are also different. From the Carboniferous to Tertiary the basin has in turn gone through rift basin, collision foreland basin, intraplate depression basin and regenerated foreland basin. Based on an analysis of thermal evolution history and buried history of the source rocks, three major periods of oil generation are found in the basin. According to the characteristics of source rock distribution, evolution, oil-source correlation, structure and multi-phase and mixed pools, the Junggar basin could be divided into 4 composite petroleum systems. Due to the variation in sedimentary facies, difference in     

Tectonic Evolution of the Junggar Foreland Basin in the Late Carboniferous-Permian

A comprehensive study has been carried out to subdivide and correlate the Upper Carboniferous and Permian sedimentary successions in the Junggar basin based on outcrops and drilling and geophysical data. The study results, combined with geological analyses of the basin's periphery and the basement, as well as studies of the sedimentary rocks within the basin, the unconformities, tectonic geometry, kinematics and geodynamics, lead to the conclusion that the Junggar basin was characterized by the development of foreland basin systems during the Late Carboniferous and Permian. During that period, three foreland basin systems were developed: (1) the northwest foreland basin system, which trended nearly north-south from Mahu to the Chepaizi Palaeo-mountain during its early stage of development and thus it was also referred to as the west foreland basin system; (2) the Karamaili foreland basin system in the east and (3) the Northern Tianshan foreland basin system in the south. These systems are different in s     

The Evolution of the Quaternary Salt Lakes in the Qaidam Basin

The paper discusses the distribution of Quaternary sediments, occurrence of saline minerals and phases of neotectonic movements and their manifestations in the Qaidam basin. The formation of four successive lacustrine terraces in Tertiary anticlinal zones in the western part of the basin was related to the neotectonic movements that took place 100 Ka ago, and the distribution of such terraces discloses, in a way. the evolutionary history of the Quaternary salt lakes. According to the distribution of the terraces coupled with the distribution of Quaternary sediments and features of salt deposition, four periods of Quaternary salt lake evolution in the basin may be distinguished, which correspond to four stages of salt deposition respectively.     

Foraminiferal sequence biostratigraphy of the Oligo‐Miocene Janjukian strata from Torquay,southeastern Australia

The foraminiferal fauna from two holes near the coastal section of marls and limestones at Torquay is dominated by inner to mid‐shelf benthic forms, especially the cibicidids, discorbids and miliolids. Planktonic species are rare and rarely age‐diagnostic. A cluster analysis of the species occurrences and relative abundances identified four assemblages, A to D up‐section. These assemblages also closely correspond to lithological changes characterising lithostratigraphic units: Angahook Formation (assemblage A), lower and upper Jan Juc Formation (B, C) and Puebla Clay (D). Biofacies trends based on the relative abundances of inner and outer neritic taxa led to the recognition of third‐order sequences and boundaries equivalent to TB1.1 to TB1.4, confirming a previous identification on sedimentological grounds. They demonstrate that foraminiferal assemblages were directly influenced by third‐order sea‐level fluctuations and can be used to predict third‐order sequences. The long‐uncertain regional Oligocene‐Miocene boundary is placed at the Jan Juc Formation—Puebla Clay contact, across which there was a major faunal change. Several benthic forms disappeared, at least temporarily: Cibicidoides perforatus, Amphistegina lessonii and Pararotalia mackayi. The typical Miocene planktonic taxa Globoquadrina dehiscens and Globoturborotalita brazieri made their first appearance. These events were associated with an increase in inner neritic benthos signalling a low sea‐level, consistent with the contemporaneous global pattern.     

Late Neogene tectonics in northwestern Victoria: Evidence from the Late Miocene–Pliocene Loxton Sand

The Late Miocene–Pliocene Loxton Sand strandplain extends across the western part of the Murray Basin in southeastern Australia. Gamma logging on groundwater bores surrounding Lake Tutchewop, which lies close to the eastern limit of this strandplain, showed that a heavy mineral layer within the Loxton Sand is displaced across the northern extension of the Leaghur Fault. A crevasse splay sand within the overlying Pliocene Shepparton Formation is also displaced, indicating that tectonic activity along the Leaghur Fault occurred in the Early Pliocene. This coincides with the Kosciusko Uplift, a major phase of Neogene tectonism across southeastern Australia, which also resulted in movement along the Danyo, Hindmarsh, Tyrell and Avoca Faults in northwestern Victoria.     

A Miocene onset of the modern extensional regime in the Isparta Angle: constraints from the Yalvaç Basin (southwest Turkey)

The pre-Neogene Tauride fold-and-thrust belt, comprising Cretaceous ophiolites and metamorphic rocks and non-metamorphic carbonate thrust slices in southern Turkey, is flanked and overlain by Neogene sedimentary basins. These include poorly studied intra-montane basins including the Yalvaç Basin. In this paper, we study the stratigraphy, sedimentology and structure of the Yalvaç Basin, which has a Middle Miocene and younger stratigraphy. Our results show that the basin formed as a result of multi-directional extension, with NE–SW to E–W extension dominating over subordinate NW–SE to N–S extension. We show that faults bounding the modern basin also governed basin formation, with proximal facies close to the basin margins grading upwards and basinwards into lacustrine deposits representing the local depocentre. The Yalvac Basin was a local basin, but a similar, contemporaneous history recently reconstructed from the Alt?napa Basin, ~100 km to the south, shows that multi-directional extension dominated by E–W extension was a regional phenomenon. Extension is still active today, and we conclude that this tectonic regime in the study area has prevailed since Middle Miocene times. Previously documented E–W shortening in the Isparta Angle along the Aksu Thrust, ~100 km to the southwest of our study area, is synchronous with the extensional history documented here, and E–W extension to its east shows that Anatolian westwards push is likely not the cause. Synchronous E–W shortening in the heart and E–W extension in the east of the Isparta Angle may be explained by an eastwards-dipping subduction zone previously documented with seismic tomography and earthquake hypocentres. We suggest that this slab surfaces along the Aksu thrust and creates E–W overriding plate extension in the east of the Isparta Angle. Neogene and modern Anatolian geodynamics may thus have been driven by an Aegean, Antalya and Cyprus slab segment that each had their own specific evolution.     

Lithostratigraphic revision and correlation of the Oligo‐Miocene Murray Supergroup,Western Murray Basin,South Australia

The Murray Basin in southeastern Australia is a large, shallow, intracratonic basin filled with laterally extensive, undeformed, Cenozoic carbonate and terrigenous clastic sedimentary rocks that constitute regional and locally important groundwater aquifers. The marine Oligo‐Miocene strata distributed throughout the southwestern portion of the basin are here encompassed within the Murray Supergroup. The Murray Supergroup (formerly Murray Group) incorporates the marginal marine marl and clay of the Ettrick Formation, Winnambool Formation and Geera Clay in the western and northern portions of the Murray Basin in South Australia, in addition to the limestone that outcrops along the banks of the River Murray in nearly continuous section for 175 km. The stratigraphic nomenclature of these rocks is revised as follows. The boundary between the lower and upper members of the Mannum Formation is redefined and a new Swan Reach Dolomite Member is erected. The Finniss Clay is revised to Finniss Formation possessing three new members: the Cowirra Clay Member, Portee Carbonate Member and Woolpunda Marl Member. The ‘Morgan Limestone’ is raised to Morgan Group and contains three new formations: the Glenforslan Formation, Cadell Formation (with Murbko Marl Member and Overland Corner Clay Member) and Bryant Creek Formation. The Pata Formation is redefined and described. Type and reference sections are erected for each new and revised unit, and are lithostratigraphically correlated to illustrate their stratigraphic architecture.     

Geochemistry of ferromanganese nodule–sediment pairs from Central Indian Ocean Basin

Fourteen ferromanganese nodule–sediment pairs from different sedimentary environments such as siliceous ooze (11), calcareous ooze (two) and red clay (one) from Central Indian Ocean Basin (CIOB) were analysed for major, trace and rare earth elements (REE) to understand the possible elemental relationship between them. Nodules from siliceous and calcareous ooze are diagenetic to early diagenetic whereas, nodule from red clay is of hydrogenetic origin. Si, Al and Ba are enriched in the sediments compared to associated nodules; K and Na are almost in the similar range in nodule–sediment pairs and Mn, Fe, Ti, Mg, P, Ni, Cu, Mo, Zn, Co, Pb, Sr, V, Y, Li and REEs are all enriched in nodules compared to associated sediments (siliceous and calcareous). Major portion of Si, Al and K in both nodules and sediments appear to be of terrigenous nature. The elements which are highly enriched in the nodules compared to associated sediments from both siliceous and calcareous ooze are Mo – (307, 273), Ni – (71, 125), Mn – (64, 87), Cu – (43, 80), Co – (23, 75), Pb – (15, 24), Zn – (9, 11) and V – (8, 19) respectively. These high enrichment ratios of elements could be due to effective diagenetic supply of metals from the underlying sediment to the nodule. Enrichment ratios of transition metals and REEs in the nodule to sediment are higher in CIOB compared to Pacific and Atlantic Ocean. Nodule from red clay, exhibit very small enrichment ratio of four with Mn and Ce while, Al, Fe, Ti, Ca, Na, K, Mg, P, Zn, Co, V, Y and REE are all enriched in red clay compared to associated nodule. This is probably due to presence of abundant smectite, fish teeth, micronodules and phillipsite in the red clay. The strong positive correlation (r ? 0.8) of Mn with Ni, Cu, Zn and Mo and a convex pattern of shale-normalized REE pattern with positive Ce-anomaly of siliceous ooze could be due to presence of abundant manganese micronodules. None of the major trace and REE exhibits any type of inter-elemental relationship between nodule and sediment pairs. Therefore, it may not be appropriate to correlate elemental behaviour between these pairs.     

Late Oligocene–Miocene mantle upwelling and interaction inferred from mantle signatures in gabbroic to granitic rocks from the Urumieh–Dokhtar arc,south Ardestan,Iran

The south Ardestan plutonic rocks constitute major outcrops in the central part of Iran’s Cenozoic magmatic belt and encompass a wide compositional spectrum from gabbro to granodiorite. U–Pb laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) dating of zircon three granodiorites yielded ages of 24.6 ± 0.1, 24.6 ± 0.1, and 24.5 ± 0.1 Ma. For tonalitic rocks, internal Rb–Sr isochron ages (biotite, feldspars) indicate cooling ages of 20.4 ± 0.1, 20.5 ± 0.1, and 22.3 ± 0.1 Ma, which are slightly younger than the zircons’ ages. The limited variations in their Sr–Nd isotope ratios indicate derivation from an asthenospheric mantle source. A geodynamic model is presented in which late Oligocene–Miocene rollback of the Neotethyan subducting slab triggered asthenospheric upwelling and partial melting in the south Ardestan. These melts were subsequently modified through fractional crystallization and minor crustal contamination en-route to the surface. Plagioclase + orthopyroxene-dominated fractional crystallization accounts for differentiation of gabbro to gabbroic diorite, whereas fractionation of clinopyroxene, titanomagnetite, and orthopyroxene led to differentiation of gabbroic diorite to diorite. Amphibole fractionation at deeper levels led to the development of tonalites.