Geoquímica en México

Geochemistry in Mexic

A positive 'amount effect' in the Sahayadri (Western Ghats) rainfall

We present stable oxygen isotopic ratios (δ18O) of rainfall collected over three years (July to October 2000- 02) at Mangalore. We observe an apparent positive correlation between the monthly, amount-weighted mean oxygen isotopic ratio of the rainwater and monthly total rainfall, contrary to the generally expected negative trend in many island and continental stations. We offer an explanation for this observation and propose that the 'amount effect' in the annual rainfall still remains with a negative slope, and thus can be useful in palaeomonsoon reconstruction using oxygen isotopic variations of annually laminated speleothems

Statistically coherent calibration of X-Ray Fluorescence Spectrometry for major elements in rocks in minerals.

We applied both the ordinary linear regression (OLR) and the new uncertainty weighted linear regression (UWLR) models for the calibration and comparison of a XRF machine through 59 geochemical reference materials (GRMs) and a procedure blank sample. )e mean concentration and uncertainty data for the GRMs used for the calibrations (Supplementary Materials) (available here) filewere achieved from an up-to-date compilation of chemical data and their processing from well-known discordancy and significance tests. )e drift-corrected XRF intensity and its uncertainty were determined from mostly duplicate pressed powder pellets. )e comparison of the OLR (linear correlation coefficient r∼0.9523–0.9964 and 0.9771–0.9999, respectively, for before and after matrix correction) and UWLR models (r∼0.9772–0.9976 and 0.9970–0.9999, respectively) clearly showed that the latter with generally higher values of r is preferable for routine calibrations of analytical procedures. Both calibrations were successfully applied to rock matrices, and the results were generally consistent with those obtained in other laboratories although the UWLR model showed mostly narrower confidence limits of the mean (slope and intercept) or lower uncertainties than the OLR. Similar sensitivity (∼2.69–46.17 kc·s1·%1 for the OLR and ∼2.78–59.69 kc·s1·%1 for the UWLR) also indicated that the UWLR could advantageously replace the OLR model. Another novel aspect is that the total uncertainty can be reported for individual chemical data. If the analytical instruments were routinely calibrated from the UWLR model, this action would make the science of geochemistry more quantitative than at present

The Morphology and Intrinsic Excitability of Developing Mouse Retinal Ganglion Cells

The retinal ganglion cells (RGCs) have diverse morphology and physiology. Although some studies show that correlations between morphological properties and physiological properties exist in cat RGCs, these properties are much less distinct and their correlations are unknown in mouse RGCs. In this study, using three-dimensional digital neuron reconstruction, we systematically analyzed twelve morphological parameters of mouse RGCs as they developed in the first four postnatal weeks. The development of these parameters fell into three different patterns and suggested that contact from bipolar cells and eye opening might play important roles in RGC morphological development. Although there has been a general impression that the morphological parameters are not independent, such as RGCs with larger dendritic fields usually have longer but sparser dendrites, there was not systematic study and statistical analysis proving it. We used Pearson's correlation coefficients to determine the relationship among these morphological parameters and demonstrated that many morphological parameters showed high statistical correlation. In the same cells we also measured seven physiological parameters using whole-cell patch-clamp recording, focusing on intrinsic excitability. We previously reported the increase in intrinsic excitability in mouse RGCs during early postnatal development. Here we showed that strong correlations also existed among many physiological parameters that measure the intrinsic excitability. However, Pearson's correlation coefficient revealed very limited correlation across morphological and physiological parameters. In addition, principle component analysis failed to separate RGCs into clusters using combined morphological and physiological parameters. Therefore, despite strong correlations within the morphological parameters and within the physiological parameters, postnatal mouse RGCs had only limited correlation between morphology and physiology. This may be due to developmental immaturity, or to selection of parameters

Ganglion Cell Adaptability: Does the Coupling of Horizontal Cells Play a Role?

Background: The visual system can adjust itself to different visual environments. One of the most well known examples of this is the shift in spatial tuning that occurs in retinal ganglion cells with the change from night to day vision. This shift is thought to be produced by a change in the ganglion cell receptive field surround, mediated by a decrease in the coupling of horizontal cells. Methodology/Principal Findings: To test this hypothesis, we used a transgenic mouse line, a connexin57-deficient line, in which horizontal cell coupling was abolished. Measurements, both at the ganglion cell level and the level of behavioral performance, showed no differences between wild-type retinas and retinas with decoupled horizontal cells from connexin57-deficient mice. Conclusion/Significance: This analysis showed that the coupling and uncoupling of horizontal cells does not play a dominant role in spatial tuning and its adjustability to night and day light conditions. Instead, our data suggest that anothe

Application Of Four Sets Of Tectonomagmatic Discriminant Function Based Diagrams To Basic Rocks From Northwest Mexico [aplicación De Cuatro Conjuntos De Diagramas Tectonomagmáticos Basados En Funciones Discriminantes A Rocas Básicas Del Noroeste De México]

Discrimination diagrams are being widely used for the past four decades to infer the tectonomagmatic affiliation of old rocks. There are several major- and trace-element composition based bivariate, ternary and multi-element discriminant function diagrams in the literature. Recent evaluation of the performance of these diagrams indicates that four sets of recent discriminant function based diagrams, in which the tectonic boundaries are determined from probability estimates for four tectonic settings of island arc, continental rift, ocean-island and mid-ocean ridge, have shown very high success rates. In this work, we have created an extensive geochemical database for on-land and off-shore basic rocks of northwest Mexico and applied these four sets of recent and highly successful tectonomagmatic discriminant function based diagrams to infer their tectonomagmatic origin. Each of these four sets of diagrams (two for major- and two for trace-elements) contained five diagrams. All the four sets of diagrams confirmed a continental rift setting for on-land basic rocks of 13 Ma age, major-element based diagrams also indicated a rift setting. However, one set of trace-element based discrimination diagrams indicated an arc to rift transition and the other set of trace- element based discrimination diagrams for the only sample from the Comondú arc, which has the required complete dataset, indicated an arc setting. All the four sets of discrimination diagrams indicated MORB setting (success rates 90%-98% and 100% for major-element and trace-element based diagrams, respectively) for off-shore rocks (most of the samples were obtained from DSDP drilled sites in the Gulf of California and some dredged rock samples from the Gulf of California) with very high success rates. All the inferred tectonic settings from these four sets of new discrimination diagrams, in general, are in conformity with those reported in the literature based on other methods. 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B.P. to the Present (1982) Journal of Geophysical Research, 87, pp. 6751-6759. , doi: 10.1029/JB087iB08p06751McDowell, F.W., Keizer, R.P., Timing of mid-tertiary volcanism in the Sierra Madre Occidental between Durango City and Mazat-lan, Mexico (1977) Geological Society of America Bulletin, 88, pp. 1479-1487. , doi:10.1130/0016-7606(1977)881479:TOMVIT2.0.CO;2McDowell, F.W., Roldán, Q.J., Amaya, M.R., Interrelationship of sedimentary and volcanic deposits associated with Tertiary extension in Sonora, Mexico (1997) Geological Society of America Bulletin, 109, pp. 1349-1360. , doi:10.1130/0016-7606(1997)1091349:IOSAVD2.3. 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Chichester: John Wiley & SonsPearce, J.A., Cann, J.R., Tectonic setting of basic volcanic rocks determined using trace element analyses (1973) Earth and Planetary Science Letters, 19, pp. 290-300. , doi: 10.1016/0012-821X(73)90129-5Pearce, J.A., Gale, G.H., Identification of ore-deposition environment from trace-element geochemistry of associated igneous host rocks (1977) Geological Society of London Special Publication, 7, pp. 14-24. , doi:10.1144/GSL.SP.1977.007.01.03Pearce, J.A., Norry, M.J., Petrogenetic implications of Ti, Zr, Y, and Nb variations in volcanic rocks (1979) Contributions to Mineralogy and Petrology, 69, pp. 33-47Pearce, T.H., Gorman, B.E., Birkett, T.C., The relationship between major element chemistry and tectonic environment of basic and intermediate volcanic rocks (1977) Earth and Planetary Science Letters, 36, pp. 121-132. , doi:10.1016/0012-821X(77)90193-5Perfit, M.R., Saunders, A.D., Fornari, D.J., Phase Chemistry, Fractional Crystallization, and Magma Mixing in Basalts from the Gulf of California, Deep Sea Drilling Project Leg 64 (2007) Deep Sea Drilling Project, 64, pp. 649-666Rogers, G., Saunders, A.D., Terrell, D.J., Verma, S.P., Marriner, G.F., Geochemistry of Holocene volcanic rocks associated with ridge subduction in Baja California, Mexico (1985) Nature, 315, pp. 389-392. , doi:10.1038/315389a0Rollinson, H.R., (1993) Using Geochemical Data: Evaluation, Presentation, Interpretation, p. 344. , Longman Scientifc Technical, EssexSaunders, A.D., Geochemistry of Basalts Recovered from the Gulf of California during Leg 65 of the Deep Sea Drilling Project (2007) Deep Sea Drilling Project, 65, pp. 591-621Saunders, A.D., Fornari, D.J., Joron, J.-L., Tarney, T.M.T., Geochemistry of Basic Igneous Rocks, Gulf of California, Deep Sea Drilling Project Leg 64 (2007) Deep Sea Drilling Project, 64, pp. 595-642Saunders, A.D., Rogers, G., Marriner, G.F., Terrell, D.J., Verma, S.P., Geochemistry of Cenozoic volcanic rocks, Baja California, Mexico: Implications for the petrogenesis of post-subduction magmas (1987) Journal of Volcanology and Geothermal Research, 32, pp. 223-245. , doi:10.1016/0377-0273(87)90046-1Shervais, J.W., Ti-V plots and the petrogenesis of modern and ophiolitic lavas (1982) Earth and Planetary Science Letters, 59, pp. 101-118. , doi:10.1016/0012-821X(82)90120-0Sheth, H.C., Do major oxide tectonic discrimination diagrams work? Evaluating new log-ratio and discriminant-analysis-based diagrams with Indian Ocean mafic volcanics and Asian ophiolites (2008) Terra Nova, 20, pp. 229-236. , doi:10.1111/j.1365-3121.2008.00811.xSolano, V.J., Moreno, F.A.P., Iriondo, A., Demant, A., Cochemé, J.-J., Middle Miocene peralkaline ignimbrites in the Hermosillo region (Sonora, Mexico): Geodynamic implications (2005) Geomaterials (Petrology), 337, pp. 1421-1430. , doi:10.1016/j.crte.2005.08.007Spencer, J.E., Normark, R., Tosco-Abreojos fault zone: A Neogene transform plate boundary within the Pacific margin of southern Baja California, Mexico (1979) Geology, 7, pp. 554-557. , doi: 10.1130/0091-7613(1979)7554:TFZANT2.0.CO;2Stock, J.M., Lee, J., Do microplates in subduction zones leave a geological record? (1994) Tectonics, 13, pp. 1472-1487. , doi:10.1029/94TC01808Till, C.B., Gans, P.B., Spera, F.J., Macmillan, I., Blair, K.D., Perils of petrotectonic modeling: A review from southern Sononra, Mexico (2009) Journal of Volcanology and Geothermal Research, 186, pp. 160-168. , doi:10.1016/j.jvolgeores.2009.06.014Vasconcelos, F.M., Verma, S.P., Rodríguez, G.J.F., Discrimi-nación tectónica: Nuevo diagrama Nb-Ba para arcos continentales, arcos insulares, "rifts" e islas oceánicas en rocas máfcas (1998) Boletín De La Sociedad Española De Mineralogía, 21, pp. 129-146Vasconcelos, F.M., Verma, S.P., Vargas, B.R.C., Diagrama Ti-V: Una nueva propuesta de discriminación para magmas básicos en cinco ambientes tectónicos (2001) Revista Mexicana De Ciencias Geológi-cas, 18, pp. 162-174Verma, S.K., Pandarinath, K., Verma, S.P., Statistical evaluation of tectonomagmatic discrimination diagrams for granitic rocks and proposal of new discriminant-function-based multi-dimensional diagrams for acid rocks (2012) International Geology Review, 54, pp. 325-347. , doi:10.1080/00206814.2010.543784Verma, S.P., Sixteen statistical tests for outlier detection and rejection in evaluation of International Geochemical Reference Materials: Example of microgabbro PM-S. Geostandards Newsletter (1997) The Journal of Geostandards and Geoanalysis, 21, pp. 59-75. , doi:10.1111/ j.1751-908X.1997.tb00532.xVerma, S.P., Geochemistry of the subducting Cocos plate and the origin of subduction-unrelated mafic volcanism at the volcanic front of the central Mexican Volcanic Bel (2000) Cenozoic Tectonics and Vol-canism of Mexico, 334, pp. 195-222. , H. Delgado-Granados, Aguirre-Díaz, G., Stock, J.M., Eds., Geological Society of America Special paperVerma, S.P., Statistical evaluation of bivariate, ternary and discriminant function tectonomagmatic discrimination diagrams (2010) Turkish Journal of Earth Sciences, 19, pp. 185-238. , doi:10.3906/yer-0901-6Verma, S.P., Geochemometrics (2012) Revista Mexicana De Ciencias Geológicas, 29 (1), pp. 276-298Verma, S.P., Agrawal, S., New tectonic discrimination diagrams for basic and ultrabasic volcanic rocks through log-transformed ratios of high field strength elements and implications for petrogenetic processes (2011) Revista Mexicana De Ciencias Geológicas, 28, pp. 24-44Verma, S.P., Díaz-González, L., Application of discordant outlier detection and separation system in geosciences (2012) International Geology Review, 54, pp. 593-614. , doi:10.1080/00206814.2011.569402Verma, S.P., Rivera-Gómez, M.A., New computer program TecD for tectonomagmatic discrimination from discriminant function diagrams for basic and ultrabasic magmas and its application to ancient rocks (2012) Journal of Iberian Geology, pp. 167-180. , doi: 10.5209/ rev_JIGE.2013.v39.n1.41757Verma, S.P., Quiroz-Ruiz, A., Critical values for six Dixon tests for outliers in normal samples up to sizes 100, and applications in science and engineering (2006) Revista Mexicana De Ciencias Geológicas, 23, pp. 133-161Verma, S.P., Quiroz-Ruiz, A., Critical values for 22 discordancy test variants for outliers in normal samples up to sizes 100, and applications in science and engineering (2006) Revista Mexicana De Ciencias Geológicas, 23, pp. 302-319Verma, S.P., Quiroz-Ruiz, A., Critical values for 33 discordancy test variants for outliers in normal samples for very large sizes of 1,000 to 30,000 (2008) Revista Mexicana De Ciencias Geológicas, 25, pp. 369-381Verma, S.P., Torres-Alvarado, I.S., Sotelo-Rodríguez, Z.T., SINCLAS: Standard igneous norm and volcanic rock classification system (2002) Computers & Geosciences, 28, pp. 711-715. , doi:10.1016/S0098-3004(01)00087-5Verma, S.P., Torres-Alvarado, I.S., Velasco-Tapia, F., A revised CIPW norm (2003) Schweizerische Mineralogische Und Petrographische Mitteilungen, 83, pp. 197-216Verma, S.P., Guevara, M., Agrawal, S., Discriminating four tectonic settings: Five new geochemical diagrams for basic and ultrabasic volcanic rocks based on log-ratio transformation of major-element data (2006) Journal of Earth System Science, 115, pp. 485-528Verma, S.P., Quiroz-Ruiz, A., Díaz-González, L., Critical values for 33 discordancy test variants for outliers in normal samples up to sizes 1000, and applications in quality control in Earth Sciences (2008) Re-vista Mexicana De Ciencias Geológicas, 25, pp. 82-96Verma, S.P., Rodríguez-Ríos, R., González-Ramírez, R., Statistical evaluation of classification diagrams for altered igneous rocks (2010) Turkish Journal of Earth Sciences, 19, pp. 239-265. , doi:10.3906/yer-0902-9Verma, S.P., Verma, S.K., First fifteen probability-based multidimensional tectonic discrimination diagrams for intermediate magmas and their robustness against post-emplacement compositional changes and petrogenetic processes (2013) Turkish Journal of Earth Sciences, , in press, doi:10.3906/yer-1204-6Verma, S.P., Verma, S.K., Pandarinath, K., Rivera-Gómez, M.A., Evaluation of recent tectonomagmatic discrimnation diagrams and their application to the origin of basic magmas in Southern Mexico and Central America (2011) Pure and Applied Geophysics, 168, pp. 1501-1525. , doi:10.1007/s00024-010-0173-2Vermeesch, P., Tectonic discrimination of basalts with classification trees (2006) Geochimica Et Cosmochimica Acta, 70, pp. 1839-1848. , doi:10.1016/j.gca.2005.12.016Vermeesch, P., Tectonic discrimination diagrams revisited (2007) Geochemistry Geophysics Geosystems, 7, pp. Q06017. , doi:10.1029/2005GC001092Vidal-Solano, J.R., Demant, A., Moreno, F.A.P., Lapierre, H., Ortega-Rivera, M.A., Lee, J.K.W., Insights into the tectonomagmatic evolution of NW Mexico: Geochronology and geochemistry of the Miocene volcanic rocks from the Pinacate area, Sonora (2008) Geological Society of America Bulletin, 120, pp. 691-708. , doi:10.1130/ B26053.1Wood, D.A., The application of a Th-Hf-Ta diagram to problems of tectonomagmatic classification and to establishing the nature of crustal contamination of basaltic lavas of the British Tertiary volcanic provinc (1980) Earth and Planetary Science Letters, 50, pp. 11-30. , doi:10.1016/0012-821X(80)90116-8Zolotarev, B.P., Margolin, E.M., Geochemistry and rare-earth element abundances of basalts from Sites 482, 483, and 485 in the Gulf of California (2007) Deep Sea Drilling Project, 65, pp. 579-59

Textural and physicochemical studies of innershelf sediments off Gangolli, west coast of India

118-122Textural and physico-chemical studies such as grain size, organic carbon, Ca and magnetic susceptibility of sediments of the innershelf off Gangolli have been carried out. The sediments are clayeysilt and siltyclay in texture. They are well-sorted, negatively skewed and leptokurtic. Multigroup descrimination analysis suggests that these sediments are derived from shallow marine origin by saltation and suspension. The amount of organic carbon and Ca increases with the depth. Organic carbon has positive correlation with Ca. The magnetic susceptibility (Xm) shows high values and has the positive correlation with mean size (Mz)

Fifteen New Discriminant-function-based Multi-dimensional Robust Diagrams For Acid Rocks And Their Application To Precambrian Rocks

For the discrimination of four tectonic settings of island arc, continental arc, within-plate (continental rift and ocean island together), and collision, we present three sets of new diagrams obtained from linear discriminant analysis of natural logarithm transformed ratios of major elements, immobile major and trace elements, and immobile trace elements in acid magmas. The use of discordant outlier-free samples prior to linear discriminant analysis had improved the success rates by about 3% on the average. Success rates of these new diagrams were acceptably high (about 69% to 97% for the first set, about 69% to 99% for the second set, and about 60% to 96% for the third set). Testing of these diagrams for acid rock samples (not used for constructing them) from known tectonic settings confirmed their overall good performance. Application of these new diagrams to Precambrian case studies provided the following generally consistent results: a continental arc setting for the Caribou greenstone belt (Canada) at about 3000. Ma, São Francisco craton (Brazil) at about 3085-2983. Ma, Penakacherla greenstone terrane (Dharwar craton, India) at about 2700. Ma, and Adola (Ethiopia) at about 885-765. Ma; a transitional continental arc to collision setting for the Rio Maria terrane (Brazil) at about 2870. Ma and Eastern felsic volcanic terrain (India) at about 2700. Ma; a collision setting for the Kolar suture zone (India) at about 2610. Ma and Korpo area (Finland) at about 1852. Ma; and a within-plate (likely a continental rift) setting for Malani igneous suite (India) at about 745-700. Ma. These applications suggest utility of the new discrimination diagrams for all four tectonic settings. 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