39. DATA REPORT: RESULTS OF GEOCHEMICAL WELL LOGGING IN THE IZU-BONEV FOREARC BASIN, SITES 782 AND 786, LEG 1251 (original) (raw)
Related papers
43. Geochemical Well Logs in the Izu-Bonin Arc-Trench System, Sites 791,792, and 793 1
Geochemical well logs were obtained in sediments at Site 791 and in both sediments and basalts at Sites 792 and 793 of Leg 126. Corrections have been applied to the logs from the latter two sites to account for variations in hole size, drilling fluid interference, and drill-pipe attenuation. Oxide and calcium carbonate weight percentages have been calculated from the processed logs and are compared to the available core measurements. Log-derived CaCO 3 measurements correlate well with shipboard CaCO 3 core measurements from Hole 79IB. In Holes 792E and 793B the log-derived oxides, with the exception of SiO 2 , agree extremely well with the X-ray fluorescence measurements.
Geochemical Well Logs in the Izu-Bonin Arc-Trench System, Sites 791, 792, and 793
Proceedings of the Ocean Drilling Program, 126 Scientific Results, 1992
Geochemical well logs were obtained in sediments at Site 791 and in both sediments and basalts at Sites 792 and 793 of Leg 126. Corrections have been applied to the logs from the latter two sites to account for variations in hole size, drilling fluid interference, and drill-pipe attenuation. Oxide and calcium carbonate weight percentages have been calculated from the processed logs and are compared to the available core measurements. Log-derived CaCO 3 measurements correlate well with shipboard CaCO 3 core measurements from Hole 79IB. In Holes 792E and 793B the log-derived oxides, with the exception of SiO 2 , agree extremely well with the X-ray fluorescence measurements.
Proceedings of the Ocean Drilling Program, 1993
Geochemical well logs were obtained in sediment at Sites 805 and 806 of Ocean Drilling Program Leg 130. Corrections have been applied to the logs to account for variations in borehole size, drilling-fluid composition, and drill-pipe attenuation. Oxide and calcium carbonate weight percentages were calculated from the logs and are compared with available carbonate measurements from core. Log-derived CaCO 3 values from Hole 805C, though lower than shipboard CaCO 3 core measurements, show a similar variation in character. In Hole 806B, log and shipboard CaCO 3 sample values have a similar mean and variance. The CaCO 3 high-resolution sample values from Hole 806B, however, have a similar mean but a lower variance than the CaCO 3 logs. It is probable that discrepancies result from gamma-ray spectrometry tool malfunctions experienced throughout the logging operations of this leg as well as from chlorine-induced interference in the calcium yield. Because the amplitude of CaCO 3 variations was extremely low (standard deviation of 1.38 on high-resolution samples), the tool, which has a sensitivity of roughly 2% for Ca, probably would not have been able to detect these variations, even if the tool had been working properly.
48. Data Report: Geochemical Well Logs Through Cenozoic Sediments From Sites 805 and 8061
Geochemical well logs were obtained in sediment at Sites 805 and 806 of Ocean Drilling Program Leg 130. Corrections have been applied to the logs to account for variations in bore-hole size, drilling-fluid composition, and drill-pipe attenuation. Oxide and calcium carbonate weight percentages were calculated from the logs and are compared with available carbonate measurements from core. Log-derived CaCO 3 values from Hole 805C, though lower than shipboard CaCO 3 core measurements, show a similar variation in character. In Hole 806B, log and shipboard CaCO 3 sample values have a similar mean and variance. The CaCO 3 high-resolution sample values from Hole 806B, however, have a similar mean but a lower variance than the CaCO 3 logs. It is probable that discrepancies result from gamma-ray spectrometry tool malfunctions experienced throughout the logging operations of this leg as well as from chlorine-induced interference in the calcium yield. Because the amplitude of CaCO 3 variations was extremely low (standard deviation of 1.38 on high-resolution samples), the tool, which has a sensitivity of roughly 2% for Ca, probably would not have been able to detect these variations, even if the tool had been working properly.
Data Report: Geochemical Results from Wireline Logs at Sites 761, 762, and 764
Proceedings of the Ocean Drilling Program, 1992
Geochemical well logs were obtained at ODP Sites 767 and 770 in the Celebes Sea. The log data obtained at sea have been corrected for borehole size changes, the effects of drilling fluids, and logging-speed variations. The processed logs are then used to calculate the amounts of the three major radioactive elements (Th, U, and K) and the dry weight percentages of oxides every 0.1524 m throughout the logged intervals. Numerous oxide core measurements were made for Site 767 and for the basement section of Site 770. Core and log measurements of CaO, A1 2 O 3 , FeO*, K 2 O, and TiO 2 agree well. At both sites, however, the log-derived SiO 2 is higher than that measured on cores. The discrepancy is due to the fact that MgO or Na 2 O could not be calculated from the logs, causing each of the elements measured by the geochemical tool to be slightly high, an effect that is most apparent in SiO 2 because it makes up the greatest portion of the rock-forming elements.
Igneous geochemistry and petrogenesis of the Izu-Bonin Forearc Basin
Major element, trace element, and radiogenic isotope compositions of samples collected from ODP Leg 126 in the Izu-Bonin forearc basin are presented. Lavas from the center of the basin (Site 793) are high-MgO, low-Ti, two-pyroxene basaltic andesites, and represent the products of synrift volcanism in the forearc region. A basement high drilled on the western flank of the basin (Site 792) comprises a series of plagioclase-rich two-pyroxene andesites with calc-alkaline affinities. These lavas are similar to calc-alkaline volcanics from Japan, but have lower contents of Ti, Zr, and low-field-strength elements (LFSE). Lavas from Site 793 show inter-element variations between Zr, Ti, Sr, Ni, and Cr that are consistent with those predicted during crystallization and melting processes. In comparison, concentrations of P, Y, LFSE, and the rare-earth elements (REE) are anomalous. These elements have been redistributed within the lava pile, concentrating particularly in sections of massive an...
27. Igneous Geochemistry and Petrogenesis of the Izu-Bonin Forearc BASIN1
www-odp.tamu.edu
Major element, trace element, and radiogenic isotope compositions of samples collected from Ocean Drilling Program Leg 126 in the Izu-Bonin forearc basin are presented. Lavas from the center of the basin (Site 793) are high-MgO, low-Ti, two-pyroxene basaltic andesites, and represent the products of synrift volcanism in the forearc region. These synrift lavas share many of the geochemical and petrographic characteristics of boninites. In terms of their element abundances, ratios, and isotope systematics they are intermediate between low-Ti arc tholeiites from the active arc and boninites of the outer-arc high. These features suggest a systematic geochemical gradation between volcanics related to trench distance and a variably depleted source.
Proceedings of the Ocean Drilling Program, 1990
During ODP Leg 107, two holes were drilled in the basement of Vavilov Basin, a central oceanic area of the Tyrrhe nian sea. Hole 655B is located near the Gortani ridge in off-axis position at the western rim of the basin; Hole 651A is located on a basement swell at the axis of the basin. This paper deals with mineral chemistry, major and trace element geochemistry, and petrogenesis of the basalts recovered in the two holes. The mineralogy of the basalts is broadly homogeneous, but all of them have suffered important seawater alteration. Their major-element compositions are similar to both normal-mid-ocean-ridge-basalts (N-MORB) and back-arc-basalts (BAB) except for Na 2 0 contents (BAB-like), and K 2 0 which is somewhat enriched in upper unit of Hole 651 A. Their affinity with N-MORB and BAB is confirmed by using immobile trace elements such as Zr, Y, and Nb. However, basalts from the two sites present contrasting geochemical characteristics on spidergrams using incompatible elements. Hole 655B basalts are homogeneous enriched tholeiites, similar to those from DSDP Hole 373 (located on the opposite side of the basin near the eastern rim), and show affinities with enriched MORB (E-MORB). At Hole 651 A, the two basalt units are chemically distinct. One sample recovered in lower unit is rather similar to those from Hole 655B, but basalts from upper unit display calc-alkaline characteristic evidenced by the increase of light-ion-lithophile-element (LILE)/ high-field-strength-element (HFSE) ratio, and appearance of a negative Nb-anomaly, making them comparable with orogenic lavas from the adjacent Eolian arc. The observed chemical compositions of the basalts are consistent with a derivation of the magmas from a N-MORB type source progressively contaminated by LILE-enriched fluids released from dehydration of the bordering subducted plate. Implications for evolution of the Tyrrhenian basin are tentatively proposed taking into consideration geochemical and chronological relationships between basalts from Leg 107 Holes 655B and 651 A, together with data from Leg 42 Site 373 and Vavilov Seamount. These data illustrate back-arc spreading in ensialic basin closely associated with the maturation of the adjacent subduction, followed by the growth of late off-axis central volcano, whereas the active sub duction retreats southeastward.
53. Data Report: Geochemical Results From Wireline Logs at Sites 761, 762, and 7641
Geochemical well logs were obtained at Sites 761, 762, and 764 of Leg 122 on the Exmouth Plateau. The preliminary log measurements which were presented in the Initial Reports have been corrected for borehole size, borehole fluids, and logging speed variations. The corrected logs are used to calculate percentages of the naturally radioactive elements and oxides of the formation. The CaCO3 logs agree well with core-derived carbonate measurements from Holes 762C and 764B, and agree less with measurements from Hole 761C. The geochemical logs are found to be useful in refining major lithologic changes in each of the three wells.