Textural studies on red sediments of Bhimunipatnam,Andhra Pradesh,east coast of India

The study presents the textural characteristics of late Quaternary red sediments of Bhimunipatnam to understand the process of formation of these sediments. The red sediments are classified into (a) yellow sediments (b) reddish brown sediments (c) brick red sediments and (d) light yellow sediments sequence in the vertical litho section. The yellow sediments, rests on the khondalite basement, comprises of medium grained, moderate to poorly sorted and positively skewed. The rounded pebble beds with trough cross bedding indicate high energy turbulent conditions of deposition. The fining upward sequences indicate sediments were deposited under decreasing energy conditions under fluvial regime.The iron bearing minerals like garnets and pyriboles have undergone chemical weathering under high oxidizing environment resulting in addition of silt and clay to the reddish brown and brick red sediments and concretions were formed by carbonate precipitation. These processes caused changes in the mean grain size and sorting nature of these sediments which are originally aeolian in origin. The light yellow sediments were medium to fine grained, well sorted and similar to modern dune sands in terms of textural parameters. These sediments were deposited under low oxidation environmental conditions and acquired yellow colour due to Fe hydroxides.     

A tectonic origin of magnetic fabric in the Shemshak Group from Alborz Mts. (northern Iran)

The magnetic lineation observed in “undeformed” sedimentary units has been interpreted either as an indication of paleoflow direction, or as a result of tectonic overprint which progressively modifies the original sedimentary fabric related to compactional processes. Distinguishing between the two processes is not always easy. In fact, most studies of the Anistropy of Magnetic Susceptibility (AMS) of “undeformed” sequences have been carried out in fine-grained sediments from foredeep sequences, which are characterized by sedimentary flow directions which are almost parallel to the main deformation structures, like thrust faults and folds. In the Alborz Mts., the Upper Triassic–Lower Jurassic Shemshak Group was deposited in a foreland to molassic basin of the Eo-Cimmerian orogen and now outcrops in several folds which are oriented parallel to the curved chain. Paleoflow directions are generally oblique to the main tectonic structures, being directed SSW to SSE and showing negligible changes in their orientation along the Alborz Mountains. We have, therefore, the opportunity to distinguish between tectonic- or sedimentary-related origins of the magnetic lineation. The AMS results show that magnetic lineations of the Shemshak Group are oriented almost parallel to the main fold axes and thrust structures, which follow the Alborz Mts. curved trend, suggesting that magnetic lineation is of tectonic origin in fine to medium grained, mostly massive sandstones, and confirming that AMS is a valuable tool to study deformation processes in sedimentary rocks.     

Environmental geochemistry of Damodar River basin, east coast of India

 Water and bed sediment samples collected from the Damodar River and its tributaries were analysed to study elemental chemistry and suspended load characteristics of the river basin. Na and Ca are the dominant cations and HCO₃ is the dominant anion. The water chemistry of the Damodar River basin strongly reflects the dominance of continental weathering aided by atmospheric and anthropogenic activities in the catchment area. High concentrations of SO₄ and PO₄ at some sites indicate the mining and anthropogenic impact on water quality. The high concentration of dissolved silica, relatively high (Na+K)/TZ⁺ ratio (0.2–0.4) and low equivalent ratio of (Ca+Mg)/(Na+K) indicate that dissolved ions contribute significantly to the weathering of aluminosilicate minerals of crystalline rocks. The seasonal data show a minimum ionic concentration in the monsoon season, reflecting the influence of atmospheric precipitation on total dissolved solids contents. The suspended sediments show a positive correlation with discharge and both discharge and suspended load reach their maximum value during the monsoon season. Kaolinite is the mineral that is possibly in equilibrium with the water. This implies that the chemistry of the Damodar River water favours kaolinite formation. The concentration of heavy metals in the finer size fraction (<37 μ m) is significantly higher than the bulk composition. The geoaccumulation index values calculated for Fe, Mn, Zn, Ni and Cr are well below zero, suggesting that there is no pollution from these metals in Damodar River sediments. Received: 21 January 1998 · Accepted: 4 May 1998     

Longshore grain size trends in the Kakinada-Mulapeta Beach,east coast of India

Shore-normal and shore-parallel variations in grain size statistics of beach sand have been studied over a period of one year along the Kakinada-Mulapeta coast. The southern beaches of this coast have been accretionary while the northern ones erosional since 125 years. The grain size gradings, beach and nearshore processes help in identifying (i) the Groins-fishing harbour beach influenced predominantly by the tidal regime. (ii) the Mulapeta-Vakalapudi beach influenced by refracted wave regime and (iii) the Vakalapudi-fishing harbour beach affected by both wave and tidal regimes at relatively subdued levels.     

Distribution of grain size, clay mineralogy and organic matter of surface sediments from Tirumalairajanar Estuary, Tamilnadu, east coast of India

The aim of this study is to understand the various sources and factors controlling the abundance and distribution of clay minerals, sand, silt, clay and organic matter of the surface sediments of Tirumalairajanar Estuary in two different seasons. The study was undertaken for two seasons, based on ten selected stations all along the estuary, mouth and freshwater zone. Furthermore, along the estuary region, clay and silt were observed and also at few stations in the upstream end. Organic matters in the sediments appeared to be the main mechanisms for the distribution of clay minerals in estuary indicated that the distributions of clay minerals were comparatively higher during postmonsoon than in premonsoon season. The clay mineral assemblage consists mainly of chlorite, kaolinite, montmorillonite, illite and very scarce gibbsite. The clay from the sediments has been separated and studied for mineral identification using X-ray diffraction analysis. The present study also reveals that sediment texture is one of the main controlling factors for the distribution of organic matter.     

Depositional features in tourist beaches of Chennai Metropolis,SE coast of India: Inferences from grain size studies

The present study was undertaken to examine the depositional and transportation pattern in the tourist beaches of Chennai in SE coast of India. Twenty four samples were analyzed for textural parameters, Linear discriminate function (LDF), C-M plots and heavy/light minerals from beach, berm and dune regions. Results of textural parameters indicate that they are coarse grained in the three regions. Majority of the samples indicate that they are moderately well sorted, symmetrically skewed and leptokurtic. The LDF analysis allowed in identifying areas that are characterized by: (1) beach, (2) shallow agitated environment and (3) fluvial deposits. C-M plots indicate that the sediments in the beaches were deposited from the near shore environment. Heavy mineral analysis suggests that the heavy and light minerals were in the range of 0.5 to 16.9% and 82.08 to 98.14% and the light/dark layers are controlled by the prevailing tidal conditions in the coastal region. It is observed that sand is accumulating from the shallow agitated environment, while the transportation and deposition of sediments is mainly due to the interaction of tidal activities at the same time. C-M plots suggest that the sediments fall in the graded suspension and the saltation activities in the region also facilitate to understand the hydrodynamics of the region suggesting that they are deposited by high-energy activities.     

A numerical study of sea breeze circulation observed at a tropical site Kalpakkam on the east coast of India, under different synoptic flow situations

A simulation study of the sea breeze circulation and thermal internal boundary layer (TIBL) characteristics has been carried out at the tropical site Kalpakkam on the east coast of India, for operational atmospheric dispersion prediction. The community based PSU/NCAR MM5 Meso-scale meteorological model is used for the study. Three cases on typical days in summer (24 May 2003), southwest (SW) monsoon (1 July 2001) winter season (2 February 2003) with different large-scale flow pattern are studied. The MM5 model is used with 3 nested domains with horizontal grid resolutions 18 km, 6 km and 2 km and 26 vertical levels. The model is integrated for 24 hours in the above cases with initial and boundary conditions taken from NCEP-FNL analyses data. Observations of 10 meteorological stations and coastal boundary layer experiments conducted at Kalpakkam are used for comparison and validation of the simulation. The characteristics of simulated sea breeze and TIBL at Kalpakkam are seen to vary in the above cases according to the prevailing large-scale winds and surface fluxes. The sea breeze circulation is seen to develop early with larger strength and inland propagation in the summer case under the influence of moderate synoptic wind and strong heating conditions than in the SW monsoon and winter cases. The horizontal and vertical extents of TIBL are found to be larger in the summer case than in other cases. Although model parameters agree in general with observations, all the fine features are not clearly captured and some slowness in model sea breeze development is also seen. The results indicate the need to improve i) the initial conditions by assimilation of available surface/upper air observations to reduce model bias and ii) surface net radiation parameterisation. The model could predict the essential features of the local circulation and further improvement is expected with better initial condition data and incorporation of more realistic surface data.     

西准噶尔“滞后型"弧岩浆作用——来自西准东部乌尔禾早二叠世中基性岩墙群的证据

西准噶尔东部哈拉阿拉特山南麓的乌尔禾地区新发现大量中基性岩墙群。岩墙群侵位于早二叠世佳木河组磨拉石建造中,展布方向与达尔布特大断裂延伸方向相一致。岩墙群岩性为辉绿岩、辉绿玢岩和辉长闪长岩,地球化学特征显示其具有低钾钙碱性玄武岩安山岩特征。稀土总量偏低(34.53×10-6~82.43×10-6),δEu(0.74~0.98)和δCe(0.98~1.15)负异常不明显,稀土元素分配模式皆呈LREE/HREE富集(LREE/HREE=2.47~7.18)的右倾型配分型式,富集K、Rb、Ba、Sr等大离子亲石元素,而高场强元素Nb、Ta强烈亏损,Zr、Hf适度亏损,具有岛弧俯冲作用的地球化学特征。正的εNd(t)值(5.51~5.71)和相对低的初始87Sr/86Sr比值(0.703 802~0.704 223)表明亏损地幔是岩墙群的源区。岩浆来自于亏损的地幔楔,且受到俯冲组分的改造。该岩墙群表明在早二叠世地表完成汇聚造山后,深部的弧岩浆作用仍在进行,所代表的"滞后型"弧岩浆作用晚于西准中西部的俯冲增生作用,表明整个西准地区俯冲造山作用结束的最终时限应在早二叠世晚期。     

Isotopic evidence of middle proterozoic magmatism from bombay high field: Implications to crustal evolution of western offshore of India

Precambrian granitic basement rocks obtained from well BH-36 of Bombay High Field, western offshore of India has been studied both by Rb-Sr and K-Ar dating methods. Seven basement samples chosen from two cores have yielded whole rock Rb-Sr isochron age of 1446 ± 67 Ma with an initial⁸⁷Sr/⁸⁶Sr ratio of 0.7062 ± 0.0012. This age has been interpreted as the formation/emplacement time of the granite. Two biotite fractions of different grain size separated from a sample CC6B2T have yielded Rb-Sr mineral isochron age of 1385 ± 21 Ma. However, these fractions when studied by K-Ar dating method have yielded slightly higher but mutually consistent ages of 1458 ± 43 Ma and 1465 ± 43 Ma, respectively. Further, two biotites separated from additional samples CC5B9T and CC6B3B have yielded K-Ar ages of 1452 ± 42 Ma and 1425 ± 40 Ma with an overall mean age of 1438 ± 19 Ma. This mean K-Ar age is indistinguishable from whole rock Rb-Sr isochron as well as mineral isochron age within experimental error. The similarity in the whole rock and biotite ages obtained by different isotopic methods suggests that no thermal disturbance has occurred in these rocks after their emplacement/formation around 1450 Ma ago. The present study provides the evidence for the existence of an important Middle Proterozoic magmatic event around 1400-1450 Ma on the western offshore of India which, hitherto, was thought to be mainly confined to the eastern Ghats, Satpura and Delhi fold belt of India. This finding may have an important bearing on the reconstruction of Proterozoic crustal evolution of western Indian shield.     

Spatial confirmation of termite mounds as Bio-geo indicator for groundwater occurrences using ground magnetic survey: A case study from Perambalur Region of Tamil Nadu,India

Termite mounds are conventionally surmised as one of the best bio-geological indicator for groundwater occurrence in places where they inhibit. Ground magnetic survey was carried out to prove the assumption about termite mounds as an important indicator for groundwater exploration. Occurrences of 18 Termite mounds were mapped using handheld GPS to identify the suitable trend for magnetic survey. After considering all the criteria such as power lines, fences and fracture system, termite mound 2, 12 and 18 were selected in the NNE-SSW trend, and the ground magnetic survey was conducted in ESE-WNW direction which is perpendicular to the trend of the termite mounds using Proton Precession Magnetometer. Totally, 99 samples were collected with 5 m sampling interval and 50 m profile interval over an area of 22 500 sq.m. The magnetic values varied from –7 363 nT to 898 nT with the mean of –331 nT. Processed map of reduction to Equator indicates the presence of NNE-SSW and WNW-ESE magnetic breaks. Analytical signal map designated the presence of magnetic low in the WNW-ESE direction which coincides spatially with the magnetic breaks. The magnetic profile lines have also brought to light the structurally weak zones. Causative body depth range was estimated using power spectrum and Euler method which are from 120 m to 40 m and <20 m to >100 m, respectively. The present study appreciably brings out the spatial relationship between the termite mounds and the hydro-fractures. This confirms the assertion with regard to termite mounds as an effective tool for groundwater exploration.     

Recent foraminifers from the inner shelf of the central West Coast,India: A reappraisal using factor analysis

Setty and Nigam (1980) had described 72 species of benthonic foraminifers from 25 inner shelf stations off central West Coast of India and the results showed somewhat patchy and anamolous distributions. This paper presents the results ofQ-mode factor analysis, which was applied to reduce the number of variables into assemblages. The analysis reveals 4 important foraminiferal assemblages.Ammonia beccarii—Ammonia annectens assemblage,Nonion boueanum—Florilus scaphum assemblage.Trochammina inflata assemblage andBulimina exilis assemblage. They can be related to freshwater run-off and organic matter contents of the sediment.     

A 100 km-long paleomagnetic traverse radial to the Sudbury Structure, Canada and its bearing on Proterozoic deformation and metamorphism of the surrounding basement

The 1850 Ma Sudbury Igneous Complex (SIC), considered to be a composite melt sheet of a major meteorite impact, has been deformed into an oval-shaped basin known as the Sudbury Structure. This paper explores to what extent this deformation has been communicated to the surrounding Archean basement around the northern margin of the SIC.Paleomagnetism of 2450 Ma Matachewan dykes and 1850 Ma impact breccia along a traverse, about 100 km-long and normal to strike of the contact between the SIC and the basement, suggests that the basement beneath the NW corner of the Sudbury Structure has been tilted to the SE within about 10 km of the contact. At this distance a possible fault separates the tilted region from one that shows no evidence of tilting. Petrographically the dykes out to a distance of about 50 km distant from the SIC are altered to upper greenschist facies of metamorphism with a fibrous amphibole replacing pyroxene and with loss of primary texture that characterizes less altered Matachewan dykes at distances greater than 50 km. The direction of magnetization found in the altered Matachewan dykes is an overprint which is probably associated with regional metamorphism related to orogenesis, or possibly with thermo-chemical alteration associated with SIC emplacement. The direction of the component is compatible with an age of about 1.8 to 1.9 Ga suggesting that the Penokean orogen is the most likely cause, if not the impact event. The paleomagnetism of the breccias, together with shatter cone orientation data, suggests that within 10 km of the SIC/basement contact, basement tilting to the southeast increases towards the SIC.     

Understanding the Mesozoic kinematic evolution in the Cameros basin (Iberian Range,NE Spain) from magnetic subfabrics and mesostructures

Analysis of anisotropy of magnetic susceptibility (AMS) and brittle mesostructures (hydroplastic synsedimentary faults and tension gashes) is applied in this study in order to characterize the Mesozoic tectonic events in the Cameros basin (NW Iberian Range), formed between Tithonian and Albian times. Low-field AMS at room and low temperature (LF-AMS at RT and LF-AMS at LT, respectively) together with high-field AMS (HF-AMS) measurements allow separating ferro- and paramagnetic fabrics. The combination of LF-AMS at LT and HF-AMS torque measurements confirms the reliability of both procedures in terms of isolating the paramagnetic contribution to the AMS. Magnetic fabric results combined with the analyses of synsedimentary faults indicate a NW–SE extension direction during Aptian (and probably Barremian) times. This extension direction is perpendicular to the main extension direction (NE–SW) prevailing during early and late stages of basin evolution. It is also consistent with extension direction deduced from large-scale bending folds and tension gashes, developed after partial lithification. Cleavage development during Albian enhanced the orientation of the magnetic fabric in lithologies where the previous extensional magnetic lineation is coaxial with the expected one for compression.     

Vulnerability from storm surges and cyclone wind fields on the coast of Andhra Pradesh,India

The results presented here are from a study conducted for the government of the state of Andhra Pradesh (GOAP) in India, as part of a World Bank project on cyclone mitigation. A set of detailed maps were prepared depicting the Physical Vulnerability (PV), specifically storm surge inundation zones are shown for frequent occurrence, 50-year return period, likely scenario for global warming and extreme global warming. Similarly vulnerable areas from strong wind field from tropical cyclones (TCS) are also presented for the same four parameters. Vulnerability zones are presented from a social point of view also based upon certain socio-economic parameters that were included in determining the overall vulnerability of each Mandal in a coastal district (a Mandal represents a group of villages and towns) include: population, senior citizens, women, children under different age groups, type of housing, income level, cyclone shelters, hospitals and medical centres, schools and caste based population. The study is about scenarios that could happen if global warming and the predicted intensification of TCS actually occur as predicted by some numerical models.     

Sedimentary structures of tidal flats: A journey from coast to inner estuarine region of eastern India

Sedimentary structures of some coastal tropical tidal flats of the east coast of India, and inner estuarine tidal point bars located at 30 to 50 kilometers inland from the coast, have been extensively studied under varying seasonal conditions. The results reveal that physical features such as flaser bedding, herringbone cross-bedding, lenticular bedding, and mud/silt couplets are common to both the environments. In fact, flaser bedding and lenticular bedding are more common in the point bar facies during the monsoon months than in the coastal tidal flat environments. Interference ripples, though common in both the environments, show different architectural patterns for different environmental domains. Interference ripples with thread-like secondary set overriding the earlier ripple-form, resembling wrinkle marks, are the typical features in estuarine point bars near the high water region. Because structures which are so far considered as key structures for near-coastal tidal flats are common to both the environments, caution should be exercised for deciphering palaeo-environments, particularly for Proterozoic rocks, where one has to depend only on physical sedimentary structures.     

苏鲁超高压变质带中海阳所地区变基性岩的地球化学性质及变质演化特征

苏鲁超高压变质带的海阳所地区广泛分布各类变基性岩,它们主要由"红眼圈"结构的变辉长岩、(石榴)斜长角闪岩组成,且以透镜状或似层状赋存于片麻岩中。根据主量元素和微量元素特征,可将海阳所地区变基性岩划分为两种类型:第一类(A组)样品轻稀土相对富集,其稀土元素配分曲线具有右倾型的特征,微量元素具有Nb、Ta、Zr、Hf、Ti的明显负异常,其蛛网图配分曲线微弱右倾,类似于岛弧玄武岩IAB的特征;第二类(B组)样品稀土元素配分曲线和微量元素蛛网图配分曲线均相对平坦,Nb、Ta、Zr、Hf、Ti略微亏损,与洋中脊玄武岩E-MORB具有一定的相似性。所有变基性岩样品均属于拉斑玄武岩系列,成因类型部分与岛弧环境相关,另一部分则可能与洋中脊环境关系密切。根据岩相学、矿物相转变、变质反应以及温压条件估算的综合研究结果,识别出海阳所变基性岩可能经历了两期变质作用,其中第一期中-高压麻粒岩相变质作用(M1)的标志性矿物组合以基质中保存的粗粒石榴石(Grt1)+粗粒单斜辉石(Cpx1)+粗粒斜长石(Pl1)±石英(Qtz)组合为特征,形成的温压条件为T=725~845℃、P=9.5~12.4kbar;第二期峰期高压麻粒岩相变质阶段(M12)以发育"红眼圈"结构为特征,典型的矿物组合为新生的细粒石榴石(Grt12)+单斜辉石(Cpx12)+斜长石(Pl12)±石英(Qtz),形成的温压条件为T=765~845℃、P=14.8~17.5kbar,而峰后角闪岩相退变质阶段(M12)以形成低温退变质矿物组合绿色角闪石(Amp22)+斜长石(Pl22)±石英(Qtz)±石榴石(Grt22)为特征,形成的温压条件为T=575~680℃、P=6.0~8.0kbar。第二期变质演化P-T轨迹具有近等温降压至减压冷却的顺时针型式。海阳所变基性岩记录的多期变质演化的信息及其P-T条件与苏鲁-大别超高压变质带存在明显差异。结合以往变基性岩新太古代-古元古代原岩年龄信息,可以判断海阳所地区的变基性岩可能来自于华北克拉通东南缘胶北地体的古老变质基底,并卷入苏鲁-大别地体中-晚三叠世造山事件中。这一重要成果对于揭示海阳所及其邻区变基性岩和围岩的成因、胶北地体古老基底的形成演化过程以及重塑苏鲁-大别超高压变质带的构造演化模式具有重要的科学意义。     

Influence of differential basement mobility on contrasting structural styles in the cover rocks: An example from Early Precambrian rocks east of Udaipur,Rajasthan

Detailed structural and lithological mapping of the Aravalli rocks overlying the Mewar Gneiss in the area east of Udaipur, Rajasthan, suggests presence of blocks bounded by faults, showing a contrasting structural pattern. The contrast is reflected in the differential development and in the orientation of AF1, AF2 and AF4 folds in different blocks. In the central Umra block, the rocks constitute a virtually homoclinal sequence showing one dominant orientation of bedding and axial planar schistosity. Fold axes, lineations andβ orientations indicate presence of reclined folds of AF1 generation. AF2 folds are either absent or have developed only locally. The two other blocks which border the Umra block show development of large AF2 synforms and local minor antiforms having N-S or NNE-SSW trend. The folds interfere with AF4 folds producing irregular domes and basins in the western Kanpur-Kalarwas Block and minor plunge reversals in Bagdara-Dhamdhar Block. It is argued that the constituents of the different blocks which formed a collage of rift basins and horsts during sedimentation, responded differentially to deforming forces because of differential mobility of the underlying basement.     

Structure and evolution of the Cauvery Shear Zone system, Southern Granulite Terrain, India: Evidence from deep seismic and other geophysical studies

The Southern Granulite Terrain with exposed Archean lower crustal rocks is studied using various geophysical tools. The crustal structure derived from seismic reflection and refraction/wide-angle reflection studies is used to understand the tectonic evolution of the region. Deep seismic reflection section along the Kolattur–Palani segment shows an oppositely dipping reflection fabric near the Moyar–Bhavani shear zone, which is interpreted as a signature of collision between the Dharwar craton and another crustal block in the south. The thickened crust due to collision was delaminated during the orogenic collapse and modified the central part, covering the Cauvery Shear Zone system, located between the Moyar–Bhavani and Karur–Oddanchatram shear zones. The delaminated lower crust is altered by magmatic underplating as evidenced by the high velocity layer just above the Moho. The velocity model of the region indicates crustal thickening at the boundary of the Dharwar craton and Moyar–Bhavani shear zone and thinning further south. Back-scattered seismic wave field with negative moveout and the Moho-offset indicate the spatial location and strike-slip nature of the shear zones. Present study suggests that the late Archean collision and suturing of the Dharwar craton with the southern crustal block at the Moyar–Bhavani shear zone may be responsible for the evolution of late Archean granulites. Late Neoproterozoic rifting is observed along the paleo-fault zones. The seismic studies constrained by gravity, magnetic and magnetotelluric data suggest that the Moyar–Bhavani and Karur–Oddanchatram shear zones of the Cauvery Shear Zone system mark terrane boundaries/suture zones.     

Magnetic measurements and pollutants of sediments from Cauvery and Palaru River,India

Rock-magnetic techniques have become a useful tool in environmental issues; in particular, magnetic studies constitute an alternative way to study pollution in different media. The present contribution focuses on magnetic parameters as pollution indicators, especially from their relationship with contents of heavy metals. The work was carried out in two Indian rivers located in Tamil Nadu, southern India. Several sediment samples were collected and studied in the laboratory using magnetic techniques, magnetic susceptibility, anhysteric remanent magnetization, isothermal remanent magnetization, and chemical techniques to determine contents of heavy metals. Magnetic mineralogy indicates the predominance of ferrimagnetic minerals; although magnetite-like minerals are the main magnetic carriers, antiferromagnetic minerals can be present as subordinate carriers. Concentration-dependent magnetic parameters revealed noticeable differences between both rivers, e.g. magnetic susceptibility is four times higher in Cauvery than in Palaru River. Moreover, such increase can be interpreted as “magnetic enhancement” and therefore related to the pollution status. This magnetic enhancement indicated a different pollutant contribution in both rivers, and also, a different spatial distribution along these rivers, where critical (or more polluted) sites were identified. On the other hand, univariate and multivariate statistical analyses—e.g. PCoordA, Multifactorial Analysis of distance, PCA and RDA—were examined, revealing a link between magnetic and chemical variables. Among magnetic parameters, the concentration-dependent magnetic parameters (e.g. magnetic susceptibility) seem to be the most relevant for this study.