EFFICIENCY OF USE CREZACIN AND ZIRCON GROWTH STIMULANTS ON SOWING QUALITIES OF SEEDS AND BIOMETRIC PARAMETERS OF SPROUTS OF KHINGAM FIR (ABIES NEPHROLEPIS)

The article presents the study of the stimulating effect of aqueous solutions of growth stimulants Crezacin and Zircon, and the identification of doses that activate the germinative energy, laboratory germination of seeds and the growth of biometric parameters of sprouts along the length and weight of Khingam fir (Abies nephrolepis). The greatest stimulating effect on the sowing qualities of Khingam fir seeds by the Crezacin and Zircon shown in the concentrations of solutions of 1∙3∙10-3–1∙6∙10-3 ml/l. Germinative energy and laboratory germination of seeds exceeded the control group by 84.8-293.9, 106.4-273.4% and 112.1-203, 59.6-187.2%, respectively. The seed quality class increased from the third to the second and first ones. The growth stimulator Crezacin had a more positive effect on the growth of sprouts along the length and weight at solution concentrations of 1∙2∙10-3–1∙6∙10-3 and 1∙2∙10-3–1∙7∙10-3 ml/l (excess to control group – 7,7–41,7 and 6,1-61,4%). Zircon is less effective. Its positive effect on the growth of the length and mass of sprouts was noted at concentrations of 1∙4∙10-3–1∙5∙10-3 and 1∙2∙10-3–1∙7∙10-3 ml/l (excess to control group – 8,3–25 and 6,1-46,5%).

Timescales of magmatism and metamorphism in the Connemara Caledonides: insights from the thermal aureole of the Dawros–Currywongaun–Doughruagh Complex, western Ireland

Zircon separates from the contact aureole of the syn-tectonic Dawros–Currywongaun–Doughruagh Complex, western Ireland, are studied to constrain the nature and timing of magmatism associated with the early stages of the Grampian Orogeny. The samples analysed come from the uppermost part of the Dalradian Supergroup in northern Connemara (the Ben Levy Grit Formation), where a laterally extensive (>10 km) package of metamorphosed siliciclastic sedimentary rocks containing heavy mineral seams crops out. The seams mainly comprise magnetite, but zircon is also present in greater than accessory quantities. The seams have been locally reworked at granulite-facies metamorphic conditions during intrusion of the Dawros–Currywongaun–Doughruagh Complex magmas. Here we combine in situ mineral chemical and U–Pb geochronological analyses of zircons from samples of these heavy mineral seams collected at different locations in the Dawros–Currywongaun–Doughruagh Complex thermal aureole. An important finding is that the zircons studied have magmatic trace-element compositions, interpreted here as a function of their growth during contact metamorphic-induced partial melting. The zircons yield a range of U–Pb spot ages whose uncertainties suggest a maximum duration of zircon growth of ˜11 Ma, between 477.1 and 466.1 Ma, though it is likely that zircon growth occurred much more quickly than this. The age constraints revealed here match well with the range of 475 to 463 Ma previously proposed for the Grampian Orogeny overall in Connemara and lend useful support to models that argue for high-intensity, relatively short-lived Grampian orogenesis in the Connemara Caledonides.

Long-lived zircon growth in trapped eclogite

<p>The residence time of rocks within subduction channels provides a narrative on the physical processes that reflect the interplay between subduction rate and angle, coupling between the lower and upper plate and hydration of the mantle wedge.  In oceanic subduction systems, it is now recognised that rocks can reside within subduction channels for 10’s of millions of years.   These apparently long-lived durations of entrainment in the subduction channel probably require circulatory motions that recover material from terminal subduction and simple one-cycle exhumation.  In turn, these residence times can plausibly be used to deduce geodynamic variables that control the subduction system.</p><p>Establishing the duration a rock has been stored within a subduction environment typically requires application of multi-mineral geochronology coupled with considerations of closure systematics.  However because subduction environments are commonly fluid-rich, a mineral with great potential to reveal durations rocks can reside within subduction channels is zircon.  In subduction environments, several studies have documented apparently long-lived records of zircon growth, but seemingly have not recognised the potential for zircon to extract information on the duration a rock experienced subduction channel metamorphism.</p><p>Lawsonite-bearing eclogite in eastern Australia has a remarkable microstructural record of zircon growth.  Thin section-scale 1-3 micron resolution synchrotron mapping by X-ray Fluorescence (XFM) reveals the presence of 1000’s of micron-sized zircons which occasionally range up to 15 microns in size.  Zircon: (1) defines inclusion trails in garnets, (2) is a foliation defining matrix mineral and (3) occurs in retrograde chlorite-bearing veins that formed during post-eclogite blueschist paragenesis.   In-situ U-Pb geochronology shows that zircon growth occurred over the interval c. 520-400 Ma.  The zircons have hydrothermal characteristics with elevated LREE and simple tetragonal morphologies.  The apparently long duration of zircon growth is generally consistent with other geochronology from the eclogite: garnet Sm-Nd and Lu-Hf ages between 530-490 Ma, matrix foliation titanite U-Pb c. 450 Ma, and matrix foliation phengite Ar-Ar and Rb-Sr ages of 460-450 Ma.   </p><p>The small size of the zircons means they cannot be readily extracted using bulk rock methods.  Instead, fast, high-resolution imaging methods such as synchrotron XFM mapping coupled with spatially precise U-Pb-trace element analysis reveal a long history of HFSE element mobility resulting in microstructurally organised zircon growth that allows rock residence time in a subduction channel to be determined.</p><p>If lawsonite eclogite from eastern Australia records more than 100 Ma of zircon growth at eclogite-blueschist facies conditions, the single eclogite sample reflects around 5000-7000 km of consumption of the palaeo-pacific plate under the east Gondwana margin while remaining trapped in the subduction channel.</p>

Polyphase Zircon Growth during Slow Cooling from Ultrahigh Temperature: an Example from the Archean Pikwitonei Granulite Domain

Quantifying the timescales of Archean ultrahigh temperature (UHT) metamorphism is essential for constraining the style of plate tectonics on the early Earth. However, such timescales can be difficult to quantify, due to the antiquity of Archean rocks and the extreme thermal conditions of UHT metamorphism. We constrain the timescales of Archean UHT metamorphic processes recorded by a single rock sample from the Pikwitonei granulite domain (northwestern Superior Province), through the integration of two U–Pb zircon petrochronologic techniques. In this study we combine: (1) high-spatial resolution laser ablation split-stream inductively coupled mass spectrometry (LASS) on in situ zircon (in thin section) and hand-picked zircon; and (2) high-precision isotope dilution thermal ionization mass spectrometry (ID-TIMS) analyses on microsampled fragments from the same hand-picked zircon analysed by LASS. Phase equilibria modelling and Zr-in-rutile thermometry suggest the rock followed a P–T path characterized by decompression at > 960 °C, followed by near-isobaric cooling at ∼0·8 GPa. In situ LASS zircon analyses could be interpreted to record zircon growth at broadly ∼2665 Ma, though the large uncertainties on isotopic dates make potentially distinct growth episodes difficult to distinguish. ID-TIMS U–Pb dates of zircon fragments reveal a polyphase zircon growth history over a 24 Ma duration, from 2673 to 2649 Ma. Zircon trace element compositions, textures, and microstructural relationships, as well as evaluation of zircon-garnet equilibrium, suggest zircon grew during melt crystallization, after UHT decompression and garnet resorption. Variable Ti concentrations within zircon domains indicate: (1) zircon crystallized through the temperature interval of ∼875 °C to ∼730 °C, potentially in isolated rock domains with variable zircon saturation temperature; and/or (2) zircon crystallized over a narrower temperature interval in isolated rock domains with variable aTiO2 and/or aSiO2. Collectively, the data suggest the west-central Pikwitonei granulite domain reached peak UHT conditions prior to 2673 Ma, after which suprasolidus conditions in the lower crust persisted for at least 24 Ma. Such an interpretation would be impossible if based on either the LASS or ID-TIMS zircon data alone, which highlights the utility of applying both techniques in tandem to constrain metamorphic timescales in ancient UHT terranes.