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The pegmatite province of the Southeastern Desert (SED) is part of a pegmatite district that extends from Egypt (extends to 1200 km2). Rare metal pegmatites are divided into (1) unzoned, Sn-mineralized; (2) zoned Li, Nb, Ta and Be-bearing; and (3) pegmatites and pegmatites containing colored, gem-quality tourmaline. The Rb/Sr data reflect a crustal origin for the rare metal pegmatites and indicate that the original SED magma was generated during the peak of regional metamorphism and predates the intrusion of post-tectonic leucogranites. These bodies developed an early border zone consisting of coarse to very coarse muscovite+quartz+alkali feldspar, followed by an intermediate zone of dominant quartz+feldspar+muscovite rock. Garnet, tourmaline, beryl, galena, pyrite, amblygonite, apatite and monazite are rare accessories in both zones. Cassiterite tends to concentrate in replacement zones and along fractures in albite+quartz+muscovite-rich portions. The highest concentrations of cassiterite occur in irregular greisenized zones which consist dominantly of micaceous aggregates of green Li-rich muscovite, quartz, albite and coarse-grained cassiterite. The different metasomatic post-solidification alterations include sodic and potassic metasomatism, greisenization and tourmalinization. Geochemically, the pegmatite-generating granites have a metaluminous composition, showing a differentiation trend from coarse-grained, unfractionated plagioclase-rich granite towards highly fractionated fine-to medium-grained, local albite-rich rock. Economically important ore minerals introduced by volatile-rich, rare metal-bearing fluids, either primarily or during the breakdown of the primary mineral assemblages, are niobium-tantalum oxides, Sn-oxides (cassiterite), Li-silicates (petalite, spodumene, euctyptite, and pollucite), Li-phosphates (amblygonite, montebrasite and lithopilite) and minor REE-minerals (Hf-zircon, monazite, xenotime, thorian, loparite and yttrio-fluorite). The pollucite is typically associated with spodumene, petalite, amblygonite, quartz and feldspar. The primary pollucite has Si/Al (at) ratios of 2.53–2.65 and CRK of 79.5–82.2. Thorian loparite is essentially a member of the loparite (NaLREETi2O6)-lueshite (NaNbO3)-ThTi2O6-ThNb4O12 quaternary system with low or negligible contents of other end-member compositions. The mineral compositionally evolved from niobian loparite to niobian thorian and thorian loparite gave rise to ceriobetafite and belyankinite with high ThO2 contents. Thorian loparite is metamict or partly metamict and upon heating regains a structure close to that of synthetic loparite NaLaTi2O6.

Xitieshanite is a new ferric sulfate mineral discovered in the oxidation zone of a Pb-Zn deposit at Xitieshan, Qinghai Province, China. The typical crystal of xitieshanite is a rhombic rectangle. It is bright green in colour with a light yellow tint. Luster vitrous Translucent to almost transparent. Streak yellow. Cleavage imperfect. Fracture uneven or conchoidal. H. (Vickers)=62.6kg/mm2. Specific gravity=1.99obs(2.02calc,) Pleochroism strong, and axial colours: X=colourless to pale yellow, Y=pale yellow, Z=light yellow with greenish tint. It is optically positive, biaxial, 2V=77°,r v. Refractive indices:N x =1.536,N y =1.570,N z =1.628. Extinction parallel and inclined. Elongation positive and negative. X-ray single-crystal study shows it is monoclinic. Space groupP21/a. Unit cell parameters:a=14.102,b=6.908,c=10.673 Å, β=111.266°,V=968.9, Å3,Z=4. The powder pattern of xitieshanite gave the strongest lines: 6.67(6)(201), 6.09(5)(110), 5.69(5)(011), 4.96(10)(002), 4.81(10)(211), 4.21(5)(112), and 3.90(9)(211). Chemical analysis gave Al2O3 0.01, Fe2O3 26.15, FeO 0.18, MgO 0.03, CaO 0.09, K2O 0.03, Na2O 0.07, SO3 27.69, H2O 45.02, total 99.27%, corresponding to the chemical formula: Fe2+ (SO4)(OH) · 7H2O. The DTA curve shows respectively three strong endothermic peaks at 85°, 170°, and 735°C, and a weak peak at 460°C. The TGA curve shows a loss of weight in three different steps. The infrared spectral curve of xitieshanite demonstrates that it has two principal absorption bands at 3,350 and 1,225–1,003 cm−1 and two subordinate bands at 1,620 and 603 cm−1.

A remarkable invariance in the ratio of 1,3-dimethylcarbazole (DMC) to 1,6-DMC was discovered in crude oils from the Pearl River Mouth Basin, South China Sea. The remarkably invariant ratio is kept at a constant of about unity regardless of their concentrations, sources or maturities for the samples. In combination with the molecular structures of 1,3- and 1,6-DMCs, the invariance might indicate that the nitrogen compounds share a common precursor with a skeleton of 1-methylcarbazole and are formed through methylation at C3 and C6 with an essentially identical rate.

The Nakora Ring Complex (NRC) (732 Ma) occurs as a part of Malani Igneous Suite (MIS) in the Western Rajasthan, India. This complex consists of three phases (volcanic, plutonic and dyke). Geochemically, the Nakora granites are peralkaline, metaluminous and slightly peraluminous. They display geochemical characteristics of A-type granites and distinct variation trends with increasing silica content. The peralkaline granites show higher concentrations of SiO2, total alkalies, TiO2, MgO, Ni, Rb, Sr, Y, Zr, Th, U, La, Ce, Nd, Eu and Yb and lower concentrations of Al2O3, total iron, Cu and Zn than metaluminous granites. AI content is ≥1 for peralkaline granites and <1 for peraluminous and metaluminous granites. Nakora peralkaline granites are plotted between 4 to 7 kb in pressure and are emplaced at greater depths (16–28 km and 480–840°C) as compared to metaluminous granites which indicate the high fluorine content in peralkaline granites. The primitive mantle normalized multi-element profiles suggest that Nakora granites (peralkaline, metaluminous and peraluminous) are characterized by low La, Sr and Eu and relatively less minima of Ba, Nb and Ti which suggests the aspects related to crustal origin for Nakora magma. The Nakora granites are characterized as A-type granites (Whalen et al., 1987) and correspond to the field of “Within Plate Granite” (Pearce et al., 1984). Geochemical, field and petrological data suggest that Nakora granites are the product of partial melting of rocks similar to Banded Gneiss from Kolar Schist Belt of India.

The procedures of sample preparation for isotopic determination of boron in clay sediments is very cumbersome, by far, there haven’t been relevant reports on that. In order to establish an effective method for sample preparation, a series of experiments were carried out. In this paper, boron in clay sediments was extracted with HCl solution and purified by two-step ion exchange method. Extracted HCl solution should be adjusted to alkalescency before passing through the Amberlite IRA 743 resin column due to the fact that Amberlite IRA 743 resin absorbs boron only from alkalescent solution. However, a mass of hydroxides of Al and Fe will be precipitated when the extracted HCl solution becomes alkalescent. Hydroxides of Al and Fe have a strong adsorption capacity for boron, which can cause boron isotope fractionation. To treat precipitated hydroxides of Al and Fe, four procedures, namely direct ion exchange (DRIE), decationizing ion exchange (DCIE), once sedimentation ion exchange (OSIE) and repeated sedimentation ion exchange (RSIE) were used and assessed. The influences of the four procedures on separation and extraction and isotopic composition of boron in experimental solutions and clay sediments were also discussed. According to the results, the DRIE, DCIE and OSIE are improper. The result of sample determination indicates that when extracting boron via RSIE, with the increase of precipitation times, there’s an obvious decrease in boron content in the precipitated hydroxides while a sharp increase in recovery of boron and it is favorable for weakening the influence of boron isotope fractionation. But the process of RSIE is time consuming and it may introduce boron. It needs further research to establish a more effective sample preparation method for isotopic determination of boron in clay sediments.

This paper is focused on a geologic “regional rift basin system pattern” and its stratigraphicalgeochemical relationship. This is mainly based on the littoral shallow marine sedimentary succession paleogeography and deposits. These successions characterize the large extensional intracratonic Chaco Paraná Basin rift system. The basin is located in South America west of the Brazilian Shield. The analyzed rift basin system evolved from the Upper Cretaceous (Late Campanian-Senonian-Maastrichtian-Early Paleocene) to Quaternary time. The siliciclastic littoral shallow marine successions were deposited from Early Senonian-Maastrichtian to Late Miocene during three main successive littoral shallow marine transgressions of continental extension. These transgressions happened over the wide pediplanized terrains of South America. These lands exist west of the more positive areas, between the Brazilian Shield and the foreland massifs that were settled in the more westernwards areas. Later, these regional foreland massifs were coupled and raised to the Andean Orogen Belt during the last 5 million years. The extensive intracratonic pediplanized low topographic relief areas were the reservoirs of siliciclastic littoral shallow marine succession deposits during the three successive widespread vast continental littoral shallow marine transgressions. The first transgression began at the Latest Campanian-Senonian and/or Early Maastrichtian time. After this episode, the sedimentary depositional systems continued during the Cenozoic until the Latest Miocene. These successions constitute a major allostratigraphic unit. The limit with underlying units is the regional unconformity between the regional volcanic event ( Jurassic-Cretacic and interleaved eolianite sandstones ) at the base and the undifferentiated Quaternary sediments ( called as the Pampeano and Post-Pampeano Formationssensu lato). Based on many facies analyses there had been checked out different levels in the eustatic sea level variations within the allostratigraphic unit. Three major stages of extensional climax were recognized and related to the stages of conspicuous eustatical sea-level variations. They happened during the Latest Senonian-Paleocene, Eocene and Miocene. The first transgression occurred during the Upper Cretaceous-Paleocene although the sedimentary deposits related to this event are scarce, which are only a few meters in thickness. However, the Upper Cretaceous-Paleocene succession is very well recognized in the actual pre-Andean zone in the north-west of Argentina and Bolivia ( the Sierras Subandinas and the meridional imbricated fault systems just joint to the actual orogen, i. e., Quebrada de Humahuaca outcrops). During the Eocene and Middle to Latest Miocene occurred the second and third extensive regional littoral shallow marine transgressions. They are present either in well log registers as in most widespread outcrops on the entire Southamerican continent. The regional analysis led to the deduction of long periods of tectonic quiescence, at least three of them. They may be inferred and synchronously related with eustatic highstand sea level variations that occurred during the Late Paleocene-Early Eocene, Latest Eocene-Early to Mid Oligocene and Middle-to-Late Oligocene-Early Miocene. The structural style is related with major extensional N-S strike faultings (regional tilted and faulting blocks). On the other hand, quite a number of strike-slip faults (mainly of regional characteristic) are present crossing the area. They have a clear influence on the accommodation and transfer zones of the rift basin system. The strike is north-west to south-east on the border of the basin, to the west, in the contact with the Pampean Ridges and the narrow-meridionally-extense Sub-Andean folded trend ( mainly Paleozoic units belonging to the so-called Sierras Subandinas geological province). Also, at the western edge of the studied area, there exist many large shear zones and upthrust faults. The strike-slip regional faults dislocated the Pampean and Sub-Andean blocks due to the interaction of crossing regional tilted and fault blocks. For this reason, anen echelon regional block model is characteristic. Incipient contaminated igneous activities were associated with this cortical weak zones. Domes, needles and necks of volcanic and sub-volcanic origin appear as the landscape of the region. A part of the igneous activity was dated on Latest Pliocene although mainly corresponding to Pleistocene and Holocene. This deduction is obvious because their morphological constitution was never eroded. The volcanic aparatous are morphologically unmodified from their extrusion to present days. All the studied successions seem to resemble a long persisting erosive, transportation and deposition episode. This phenomenon is linked to a large regional (continental) unconformity dated at Late Cretaceous. The entire analyzed sedimentary succession deposits and their siliciclastic facies associations correspond clearly to a “heterolithic facies succession” which is very common within persisting tide-dominated depositional systems ( passive margins ). In fact, this is what happened during Cenozoic times ( Torra, 1998b, 2001a). The heterolithic Miocene facies deposits constitute one of the best continental exposed examples. Paleogeographical evidence showed that the Paranense and Amazonic Sea transgressions had been a littoral shallow marine connection during long time from Middle to Late Miocene. During the Late Cretaceous and Eocene periods marine connections were also active in the region. This fact is strongly supported by the tectonic and geomorphological framework of the proto-Southamerican continent, fossil remains and similar sedimentary deposits. The geochemical results showed an outstanding similarity among the three sandy-muddy successions herein studied. Both major and trace elements always show the same geochemical patterns. Specially mentioned are the elements gallium, cesium, chromium, barium, vanadium, thorium, zirconium, rubidium and strontium because they present very constant values through all successions. The Paranense and Amazonic epicontinental seas had been connected to the Pacific Ocean during the three marine episodes. The connections were formed by narrow inter-mountain valleys, present in the pre-Andean foreland massifs. These events occurred prior to the main orogenesis elevation of the Andean orogen belt in the last 5 to 1 Ma ( Pliocene-Latest Pleistocene ). This paper shows, for the first time, a synthetic stratigraphical-geochemical “regional model” for the Chaco Paraná Basin rift system which should be largely improved in later studies. The Chaco Paraná Basin carries many unexamined-unexplored natural resources which need more regional and local studies for their evaluation. This is in spite of the area that has the problem of a significative vegetation coberture and scarce good outcrops. The development of modern techniques of data-acquisition will help to overcome these difficulties.