Plagioclase weathering by mycorrhizal plants in a Ca-depleted catchment, inferred from Nd isotope ratios and REE composition

2017 ◽  
Vol 51 (6) ◽  
pp. 537-550
Author(s):  
Tasuku Akagi ◽  
Tomohiro Miura ◽  
Rie Takada ◽  
Kazuo Watanabe
Keyword(s):  
Isotope Ratios ◽  
Nd Isotope ◽  
Mycorrhizal Plants

New approaches to crustal evolution studies and the origin of granitic rocks: what can the Lu-Hf and Re-Os isotope systems tell us?

1996 ◽  
Vol 87 (1-2) ◽  
pp. 339-352 ◽  
Author(s):  
Clark M. Johnson ◽  
Steven B. Shirey ◽  
Karin M. Barovich
Keyword(s):  
Continental Crust ◽  
Isotope Ratios ◽  
Granitic Rocks ◽  
Nd Isotope ◽  
Volcanic Arcs ◽  
Depleted Mantle ◽  
Os Isotopes ◽  
Isotope System ◽  
Os Isotope

ABSTRACT:The Lu-Hf and Re-Os isotope systems have been applied sparsely to elucidate the origin of granites, intracrustal processes and the evolution of the continental crust. The presence or absence of garnet as a residual phase during partial melting will strongly influence Lu/Hf partitioning, making the Lu–Hf isotope system exceptionally sensitive to evaluating the role of garnet during intracrustal differentiation processes. Mid-Proterozoic (1·1–1·5Ga ) ‘anorogenic’ granites from the western U.S.A. appear to have anomalously high εHf values, relative to their εNd values, compared with Precambrian orogenic granites from several continents. The Hf-Nd isotope variations for Precambrian orogenic granites are well explained by melting processes that are ultimately tied to garnet-bearing sources in the mantle or crust. Residual, garnet-bearing lower and middle crust will evolve to anomalously high εHf values over time and may be the most likely source for later ‘anorogenic’ magmas. When crustal and mantle rocks are viewed together in terms of Hf and Nd isotope compositions, a remarkable mass balance is apparent for at least the outer silicate earth where Precambrian orogenic continental crust is the balance to the high-εHf depleted mantle, and enriched lithospheric mantle is the balance to the low-εHf depleted mantle.Although the continental crust has been envisioned to have exceptionally high Re/Os ratios and very radiogenic Os isotope compositions, new data obtained on magnetite mineral separates suggest that some parts of the Precambrian continental crust are relatively Os-rich and non-radiogenic. It remains unclear how continental crust may obtain non-radiogenic Os isotope ratios, and these results have important implications for Re-Os isotope evolution models. In contrast, Phanerozoic batholiths and volcanic arcs that are built on young mafic lower crust may have exceptionally radiogenic Os isotope ratios. These results highlight the unique ability of Os isotopes to identify young mafic crustal components in orogenic magmas that are essentially undetectable using other isotope systems such as O, Sr, Nd and Pb.

Zircon U-Pb ages, geochemistry, and Sr-Nd isotope ratios for early cretaceous magmatic rocks, southern Saqqez, northwestern Iran

Geochemistry ◽  
2020 ◽  
pp. 125687
Author(s):  
Somayeh Gholipour ◽  
Hossein Azizi ◽  
Fariborz Masoudi ◽  
Yoshihiro Asahara ◽  
Motohiro Tsuboi
Keyword(s):  
Early Cretaceous ◽  
Isotope Ratios ◽  
Nd Isotope ◽  
Magmatic Rocks ◽  
Northwestern Iran

scholarly journals Sr and Nd isotope ratios and REE abundances of moraines in the mountain areas surrounding the Taklimakan Desert, NW China.

2000 ◽  
Vol 34 (6) ◽  
pp. 407-427 ◽  
Author(s):  
Qing Chang ◽  
Takashi Mishima ◽  
Sadayo Yabuki ◽  
Yoshio Takahashi ◽  
Hiroshi Shimizu
Keyword(s):  
Isotope Ratios ◽  
Taklimakan Desert ◽  
Mountain Areas ◽  
Nd Isotope ◽  
Nw China ◽  
The Taklimakan Desert

scholarly journals Climate induced temporal change in Sr-Nd isotope ratios in the valley-fill deposits of the Ganga river

2014 ◽  
Vol 48 (5) ◽  
pp. 451-462 ◽  
Author(s):  
SHAILESH AGRAWAL ◽  
PRASANTA SANYAL ◽  
SRINIVASAN BALAKRISHNAN ◽  
JITENDRA K. DASH
Keyword(s):  
Temporal Change ◽  
Isotope Ratios ◽  
Ganga River ◽  
Nd Isotope ◽  
Valley Fill

Metabasite from the Variscan belt in NE Sardinia, Italy: within-plate OIB-like melts with very high Sr and low Nd isotope ratios

2010 ◽  
Vol 22 (4) ◽  
pp. 509-523 ◽  
Author(s):  
Gabriele Cruciani ◽  
Andrea Dini ◽  
Marcello Franceschelli ◽  
Mariano Puxeddu ◽  
Daniela Utzeri
Keyword(s):  
Isotope Ratios ◽  
Variscan Belt ◽  
Nd Isotope ◽  
Very High

Glacial-to-interglacial variations in the deep water at the Bermuda Rise inferred from a Nd isotope record covering the last million years

2020 ◽  
Author(s):  
Maria Jaume-Seguí ◽  
Joohee Kim ◽  
Karla P. Knudson ◽  
Maayan Yehudai ◽  
Steven L. Goldstein ◽  
...  
Keyword(s):  
North Atlantic ◽  
Deep Water ◽  
Isotope Ratios ◽  
Nepheloid Layer ◽  
Nd Isotope ◽  
Isotope Signature ◽  
The North ◽  
The North Atlantic ◽  
Gyre System ◽  
Bermuda Rise

<p>The formation of North Atlantic Deep Water (NADW) in the North Atlantic is an important modulator of the climate system, as it drives the global termohaline circulation, responsible for the distribution of heat, salts and nutrients across the oceans. ODP Site 1063 (4584 m), on the deep Bermuda Rise, is located in the mixing zone between NADW and Antarctic Bottom Water (AABW) and appears to be a good location to study how ocean circulation and climate interconnect. Here we present a new record based on Nd isotope ratios that covers ~1 Ma at that Site. Our data shows Nd isotope ratios during parts of interglacials that are much lower than present day NADW. These results are coherent with recent published studies on the last interglacial–glacial cycle that show that the deep North Atlantic Nd isotope ratios are also lower than NADW during the early interglacial. However, Nd isotope values from the shallower DSDP Site 607 (3427 m), within the core of NADW, have remained similar to modern NADW during interglacials over the same time interval. Site 607 is thought to represent the deep North Atlantic, as shown by an Atlantic meriodional transect that displays Nd isotopes ratios for glacial and interglacial maxima over the last ~1 Ma. We suggest that Nd isotope ratios at Site 1063 do not fully represent the North Atlantic endmember of the AMOC during interglacials, but regional or local processes. However, glacial values at Site 1063 fitting those of Site 607 suggest that Nd isotope ratios represent, indeed, water mass mixing during glacial periods. The low Nd-isotope ratios in the deep Bermuda Rise during interglacials would be the result of particle-seawater exchange derived from the arrival of freshly ground, poorly weathered bedrock from the Canadian shield to the North Atlantic during major ice sheet retreats, such as deglaciations as well as stadial-to-interstadial transitions. Consequently, a deep, regionally constrained layer of seawater is tagged with this extreme Nd isotope signature that is not representative of the AMOC. We suggest that a benthic nepheloid layer, whose development is driven by a deep-recirculating gyre system regulated by the interaction between the northward flowing Gulf Stream and the southward flowing deep western boundary current, facilitates the periodical masking of the deep Atlantic Nd isotope signature at Site 1063. The intermittence of the masking allows for a speculation on how the deep-recirculating gyre system might have changed over the last ~1 Ma glacial-to-interglacial cycles.</p>

Spatial variations of Sr and Nd isotope ratios of Cretaceous-Paleogene granitoid rocks, Southwest Japan Arc

1992 ◽  
Vol 112 (2-3) ◽  
pp. 165-177 ◽  
Author(s):  
H. Kagami ◽  
S. Iizumi ◽  
Y. Tainosho ◽  
M. Owada
Keyword(s):  
Isotope Ratios ◽  
Spatial Variations ◽  
Southwest Japan ◽  
Nd Isotope ◽  
Granitoid Rocks
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