Globally distributed iridium layer preserved within the Chicxulub impact structure

The Cretaceous-Paleogene (K-Pg) mass extinction is marked globally by elevated concentrations of iridium, emplaced by a hypervelocity impact event 66 million years ago. Here, we report new data from four independent laboratories that reveal a positive iridium anomaly within the peak-ring sequence of the Chicxulub impact structure, in drill core recovered by IODP-ICDP Expedition 364. The highest concentration of ultrafine meteoritic matter occurs in the post-impact sediments that cover the crater peak ring, just below the lowermost Danian pelagic limestone. Within years to decades after the impact event, this part of the Chicxulub impact basin returned to a relatively low-energy depositional environment, recording in unprecedented detail the recovery of life during the succeeding millennia. The iridium layer provides a key temporal horizon precisely linking Chicxulub to K-Pg boundary sections worldwide

Development of methods for Mg, Sr and Pb isotopic analysis of crude oil by MC-ICP-MS : addressing the challenges of sample decomposition

New approaches in isotope geochemistry require the development of novel methods for the isotopic analysis of crude oil, a typically complex and very hard to digest organic geological matrix. In this work, methods were developed for the determination of isotope ratios of Mg, Sr and Pb in crude oil by multi-collector inductively coupled plasma-mass spectrometry (MC-ICP-MS). Two sample preparation methods, (i) microwave-assisted wet digestion within an ultra-high pressure digestion cavity (MAWD-PDC) and (ii) solubilization of inorganic solids as obtained after the ASTM D4807 test method, were evaluated. Using MAWD-PDC, up to 0.5 g of crude oil was efficiently digested using only 6 mL of 14.4 mol L-1 HNO3 (75 min, temperature up to 250 degrees C). MAWD-PDC was shown to be a suitable sample preparation method for subsequent determination of Mg, Sr and Pb isotope ratios. On the other hand, the ASTM method does not require sophisticated equipment. With this approach up to 10 g of oil can be dissolved in toluene and filtered through a nylon membrane and elements present as inorganic solids, such as Mg and Sr, are retained on the membrane and can be easily recovered in water. However, Pb was not recovered. Column chromatographic protocols for target element isolation were fine-tuned for each analyte to ensure quantitative yields. No statistical difference was observed between the results for Mg and Sr isotope ratios obtained using both sample preparation methods. A proof-of-concept study showed that the Mg-Sr-Pb isotopic composition of the Brazilian crude oils was within the range observed for seawater and the deposit bedrock, suggesting that the methods developed can be considered as promising tools to decipher the formation history of oil reservoirs

Ablation features of glass and steel and their effect on LA-ICP-MS analysis results

Проведено исследование влияния параметров излучения на относительные чувствительности определения элементов-примесей при анализе стеклянной и стальной матриц методом масс-спектрометрии с индуктивно связанной плазмой в сочетании с лазерной абляцией. Показано, что коэффициенты относительной чувствительности элементов-примесей при изменении плотности мощности лазера зависят не только от их физико-химических свойств (температура плавления, летучесть, потенциал ионизации и др.), но и от особенностей лазерной абляции исследуемых материалов. Геометрия образующихся кратеров наглядно демонстрирует различие процессов теплопередачи энергии излучения лазера при воздействии на стальную и стеклянную матрицы.The effect of laser emission parameters on relative sensitivities of elements-admixtures was investigated during laser-ablation inductively coupled plasma mass-spectrometry analysis of steel and glass matrix. It was shown that variation of the intensity of laser radiation influence on relative sensitivity factors (RSF) of elements to be determined to a variable extend. The shape of ablation craters demonstrates differences of heat transport of laser energy to the steel and glass matrix. The processes occurred during laser sampling has an impact on relative sensitivities of elements

Determination of major and trace elements by inductively coupled mass-spectrometry in silicate rocks after fusion with LiBo₂

Оценена возможность одновременного определения широкого набора элементов методом масс-спектрометрии с индуктивно-связанной плазмой (ИСП-МС) в силикатных породах после сплавления с метаборатом лития. Работа выполнена на стандартных образцах состава естественных горных пород. Определение всех элементов осуществляется в рамках одного измерения в режимах низкого, среднего и высокого разрешения масс-спектрометра c магнитным сектором ELEMENT с использованием внешней градуировки по стандартному образцу BHVO-1 и применением внутреннего стандарта. Правильность разработанной методики подтверждена сравнением результатов, полученных для 9 стандартных образцов, с принятыми значениями. Погрешность определения всех элементов в установленном диапазоне концентраций существенно не различается и составляет менее 10 %.The ability of simultaneous determination of great number of elements by inductively coupled plasma mass-spectrometry (ICP-MS) has been estimated in silicate rocks after fusion with LiBO₂. The objects of analysis were geological reference materials. Simultaneous determination of all elements is carried out in low, medium and high resolution using high resolution mass-spectrometer ELEMENT with external calibration of the reference material - BHVO-1 and the internal standard. The method has been validated through the analysis of nine geological reference materials. Relative standard deviations for all elements were lower than 10 % in the defined concentrations range and did not differ for the major and trace elements

Isotopic evolution of planetary crusts by hypervelocity impacts evidenced by Fe in microtektites

Fractionation effects related to evaporation and condensation had a major impact on the current elemental and isotopic composition of the Solar System. Although isotopic fractionation of moderately volatile elements has been observed in tektites due to impact heating, the exact nature of the processes taking place during hypervelocity impacts remains poorly understood. By studying Fe in microtektites, here we show that impact events do not simply lead to melting, melt expulsion and evaporation, but involve a convoluted sequence of processes including condensation, variable degrees of mixing between isotopically distinct reservoirs and ablative evaporation during atmospheric re-entry. Hypervelocity impacts can as such not only generate isotopically heavy, but also isotopically light ejecta, with δ56/54Fe spanning over nearly 5‰ and likely even larger variations for more volatile elements. The mechanisms demonstrated here for terrestrial impact ejecta modify our understanding of the effects of impact processing on the isotopic evolution of planetary crusts

Globally distributed iridium layer preserved within the Chicxulub impact structure.

The Cretaceous-Paleogene (K-Pg) mass extinction is marked globally by elevated concentrations of iridium, emplaced by a hypervelocity impact event 66 million years ago. Here, we report new data from four independent laboratories that reveal a positive iridium anomaly within the peak-ring sequence of the Chicxulub impact structure, in drill core recovered by IODP-ICDP Expedition 364. The highest concentration of ultrafine meteoritic matter occurs in the post-impact sediments that cover the crater peak ring, just below the lowermost Danian pelagic limestone. Within years to decades after the impact event, this part of the Chicxulub impact basin returned to a relatively low-energy depositional environment, recording in unprecedented detail the recovery of life during the succeeding millennia. The iridium layer provides a key temporal horizon precisely linking Chicxulub to K-Pg boundary sections worldwide

Globally distributed iridium layer preserved within the Chicxulub impact structure

The Cretaceous-Paleogene (K-Pg) mass extinction is marked globally by elevated concentrations of iridium, emplaced by a hypervelocity impact event 66 million years ago. Here, we report new data from four independent laboratories that reveal a positive iridium anomaly within the peak-ring sequence of the Chicxulub impact structure, in drill core recovered by IODP-ICDP Expedition 364. The highest concentration of ultrafine meteoritic matter occurs in the post-impact sediments that cover the crater peak ring, just below the lowermost Danian pelagic limestone. Within years to decades after the impact event, this part of the Chicxulub impact basin returned to a relatively low-energy depositional environment, recording in unprecedented detail the recovery of life during the succeeding millennia. The iridium layer provides a key temporal horizon precisely linking Chicxulub to K-Pg boundary sections worldwide