DefinitionsBatch Melting: The melt remains resident until at some point it is released and moves upward; Equilibrium melting process with variable %melting.

Adiabatic Process: a process that occurs without the transfer ofheator matter between a system and its surroundings.[1][2]A key concept inthermodynamics, adiabatic transfer provides a rigorous conceptual basis for the theory used to expound thefirst law of thermodynamics. It is also key in a practical sense, that many rapid chemical and physical processes are described using the adiabatic approximation; such processes are usually followed or preceded by events that do involve heat transfer.Adiabatic processes are primarily and exactly defined for a system contained by walls that are completely thermally insulating and impermeable to matter; such walls are said to beadiabatic. Anadiabatic transferis a transfer of energy as work across an adiabatic wall or sector of a boundary.Approximately, a transfer may be regarded as adiabatic if it happens in an extremely short time, so that there is no opportunity for significant heat exchange.[3]

Incremental Batch Melting: Calculate batch melting for successive batches (same equation); Must recalculate Di as solids change as minerals are selectively melted (computer programs e.g. MELTS)

Half-Life: the time required, probabilistically, for half of the unstable, radioactiveatomsin a sample to undergoradioactive decay.Low-Velocity Zone: Thelow-velocity zone(LVZ) occurs close to the boundary between thelithosphereand theasthenospherein the uppermantle. It is characterized by unusually lowseismic shear wavevelocity compared to the surrounding depth intervals. This range of depths also corresponds to anomalously high electrical conductivity.It is present between about 80 and 300km depth. This appears to be universally present for S waves, but may be absent in certain regions for P waves.[2]A second low-velocity zone (not generally referred to as the LVZ, but asULVZ) has been detected in a thin 50km layer at thecore-mantle boundary.[3]These LVZs may have important implications for plate tectonics and the origin of the Earth's crust.[2][3][4]The LVZ has been interpreted to indicate the presence of a significant degree ofpartial melting, and alternatively as a natural consequence of a thermal boundary layer and the effects of pressure and temperature on the elastic wave velocity of mantle components in the solid state.[2]In any event, a very limited amount of melt (about 1%) is needed to produce these effects. Water in this layer can lower the melting point, and may play an important part in its composition

Primary Melt/MagmaWhen a rock melts, the liquid is aprimary melt. Primary melts have not undergone any differentiation and represent the starting composition of a magma. In nature it is rare to find primary melts. The leucosomes ofmigmatitesare examples of primary melts. Primary melts derived from the mantle are especially important, and are known asprimitive meltsor primitive magmas. By finding the primitive magma composition of a magma series it is possible to model the composition of the mantle from which a melt was formed, which is important in understanding evolution of themantle.Parental Melt/MagmaWhere it is impossible to find the primitive or primary magma composition, it is often useful to attempt to identify a parental melt. A parental melt is a magma composition from which the observed range of magma chemistries has been derived by the processes of igneous differentiation. It need not be a primitive melt.For instance, a series of basalt flows are assumed to be related to one another. A composition from which they could reasonably be produced by fractional crystallization is termed aparental melt. Fractional crystallization models would be produced to test the hypothesis that they share a common parental melt.At high degrees of partial melting of the mantle,komatiiteandpicriteare produced.

Marine GeochemistryRedfield RatiosThe uptake of nutrients from surface waters and their release into deep water from falling organic particles imposes a verti-cal gradient on the concentration on nutrients in the ocean (Figure 15.13). Redfield (1958) found that C, N, and P were present in living tissue in nearly constant proportions of 106:16:1. These are called the Redfield ratios (more recent work suggests that marine organic matter is actually richer in carbon and just slightly poorer in nitrogen, with the best current estimate of the Redfield ratios being about 126:16:1). Thus we would expect the concentration of phosphate and nitrate to be highly correlated in seawater, and this is indeed the case. N and P concentrations in seawater is the same as that ratio of oceanic organic matter. All P and N in the shallow ocean comes from the mineralisation of organic matter at depth, so it is supplied to the cycle with the Redfield ratio. Classification of elements based on how they behave in ocean:Conservative elements vary exactly like salinity, i.e. only by dilution and concentration. In principle there are no sinks. In principle the residence time is infinite.Nutrient elements are essential for life and are stripped efficiently out of shallow waters where productivity is high, then regenerated at depth by respiration or decay of falling organic matter. The residence time in the shallow ocean is very short but in the whole ocean is long. Scavenged elements are supplied at the surface but are readily adsorbed onto particles and removed by sedimentation. The residence time is short. Often classified as S/N.What makes a good stable isotope? The elements have a relatively low atomic mass - measurable separation The relative difference between rare (heavy and abundant (light) isotope is large These elements form chemical bonds that have a high degree of covalent character Forms compounds with a high variety of bonding neighbours (many oxidative states) Rare isotope is a small fraction of total (0.05 Rare isotope is a small fraction of total (0.05 5%) to ensure precise determinations of isotopic ratios by mass spectrometry Abundant in nature. Biogenic elements - Abiogenic substanceis a substance produced bylifeprocesses. It may be either constituents, or secretions, ofplantsoranimalsStable Isotopes Ocean colder waters tend to have higher values (+3.5), that is, they are O-18 enriched, while warmer waters have lower values (0 to 2), that is, they are O-18 depleted. A fraction of the biogenic particles produced in surface water survives degradation or dissolution in the deep sea and gradually accumulates on the seafloor. paleoceanographers are attempting to make use of the contrasting behavior of the two natural radionuclides thorium 230 and protactinium 231. Weathering removes uranium from crustal rocks and rivers transport it to the ocean, which has a uniform uranium concentration everywhere. Two primary uranium (U) isotopes, U-238 and U-235, initiate different decay series and produce daughters with distinct properties (Fig. 3). Among these daughters, thorium 230 (Th-230) and protactinium 231 (Pa-231) are particularly useful for late Quaternary paleoceanography. Unlike their parent uranium isotopes, Th-230 and Pa-231 are very insoluble in seawater. They are rapidly adsorbed onto settling particles and removed to the underlying sediments through a process called "scavenging." The basic principles to understand are source, means of transport, rate of supply, and potential for dissolution or change on the sea floor. The basic sources of the sediments found in the deep sea are erosion from land , eruption of volcanoes, production by pelagic organisms , and cosmic fallout. Means of transport, which applies mostly to sediments eroded from land, refers to whether the sediments were dispersed out over the oceans by wind, were transported to the deep sea by gravity flows, were conveyed far from shore by surface currents before settling out of suspension, or were carried and dropped by melting ice. Rates of supply for sediments eroded from land or erupted by volcanoes declines with distance from a source. Rates and types of production by pelagic organisms vary with nutrient supplies and temperature in the surface waters of the ocean. Potential for dissolution or change depends upon the chemistry of the water in the deep sea and in the deep-sea sediments themselves. Dissolved load Supply source Turbidity currents Dissolution in bottom waters affect carbonates accumulation rates in the deep sea Circulation of deep bottom waters is driven by four main factors: formation in source regions, deep-sea topography, interocean connections, and the Earth's rotation. Thermohaline circulation is density driven as the most dense waters flow along the bottom of the deepest parts of the ocean. The effect of the Earth's rotation, the Coriolis effect, accelerates currents along the western sides of basins. Current flow is also accelerated over any topographic high or through any constriction or passageway. While most of the deep sea floor experiences rather slow currents (less than 2 cm/sec), current velocities of 10-15 cm/sec and higher have been recorded in areas of current acceleration. Furthermore, current velocities at midwater depths can be 2-3 times those on the bottom, so current velocities over seamounts can be strongly erosional.Factors influencing marine oxygen-18 record.- varies between glacial and interglacial periods (isotopically light water was stored in glaciers, thus enriching the oceans in 18O.) will show zig/zag pattern on an O-18 vs Time graph1. Condensation and evaporation hence, composition of seawater2. Variation in the earths orbit eccentricity (degree to which orbit differs from circular) and tilt; precession (change in theorientationof the rotational axis of arotatingbody) affects eccentricity3. Variation in the solar energy flux insolation4. Temperature Fractionation between H2180 and H2160 molecules during evaporation concentrates the H2 O-16 molecules in the water vapor, leaving the water enriched in H2180 molecules. Conversely, fractionation during condensation concentrates the H2180 molecules in the precipitation (rain/snow), further enriching the clouds (water vapor) in H2160 molecules relative to H2180 moleculeThe most important fact is that for the last 40,000 years, the 18Ocalcit e changes have been demonstrated to be globally synchronous by AMS (accelerator mass spec) 14C datingLast 3 million years :Onset of Pleistocene glaciations with formation of permanent ice sheets at high northern latitudes. As the ice sheets waxed and waned, the concomitant fall and rise of sea level left direct evidence for the intensity and timing of glacial cycles. The major sea-level cycles occur at intervals of ~100,000 years (100 kyr) over the past ~800 kyr, with maximum amplitudes of 120140 m, involving changes in ice volume of 5060 million km3. Superimposed on these are lesser cycles of a few tens of thousands of years and shorter duration. The oscillations between glacial and interglacial climate conditions over the past three million years have been characterized by a transfer of immense amounts of water between two of its largest reservoirs on Earth the ice sheets and the oceans. Since the latest of these oscillations, the Last Glacial Maximum (between about 30,000 and 19,000 years ago),50 million cubic kilometres of ice has melted from the land-based ice sheets, raising global sea level by130 metres. Such rapid changes in sea level are part of a complex pattern of interactions between the atmosphere, oceans, ice sheets and solid earth, all of which have different response timescales. The trigger for the sea-level fluctuations most probably lies with changes in insolation, caused by astronomical forcing, but internal feedback cycles complicate the simple model of causes and effects.

Connection between isotopes and temperature/weather[edit]18O is twoneutronsheavier than16O and causes the water molecule in which it occurs to be heavier by that amount. The addition of more energy is required tovaporizeH218O than H216O, and H218O liberates more energy when itcondenses. In addition, H216O tends to diffuse more rapidly.Because H216O requires less energy to vaporize, and is more likely to diffuse to the liquid surface, the first water vapor formed during evaporation of liquid water is enriched in H216O, and the residual liquid is enriched in H218O. When water vapor condenses into liquid, H218O preferentially enters the liquid, while H216O is concentrated in the remaining vapor.As an air mass moves from a warm region to a cold region, water vapor condenses and is removed as precipitation. The precipitation removes H218O, leaving progressively more H216O-rich water vapor. This distillation process causes precipitation to have lower18O/16O as the temperature decreases. Additional factors can affect the efficiency of the distillation, such as the direct precipitation of ice crystals, rather than liquid water, at low temperatures.Due to the intense precipitation that occurs in hurricanes, the H218O is exhausted relative to the H216O, resulting in relatively low18O/16O ratios. The subsequent uptake of hurricane rainfall in trees, creates a record of the passing of hurricanes that can be used to create a historical record in the absence of human records.[1]Connection between temperature and climate[edit]The18O/16O ratio provides a record of ancient water temperature. Water 10 to 15C(18 to 27F) cooler than present representsglaciation. As colder temperatures spread toward the equator, water vapor rich in18O preferentially rains out at lower latitudes. The remaining water vapor that condenses over higher latitudes is subsequently rich in16O.[2]Precipitation and therefore glacial ice contain water with a low18O content. Since large amounts of16O water are being stored as glacial ice, the18O content of oceanic water is high. Water up to 5C (9F) warmer than today represents an interglacial, when the18O content of oceanic water is lower. A plot of ancient water temperature over time indicates that climate has varied cyclically, with large cycles andharmonics, or smaller cycles, superimposed on the large ones. This technique has been especially valuable for identifying glacial maxima and minima in thePleistocene.Connection between calcite and water[edit]Limestoneis deposited from thecalciteshells of microorganisms. Calcite, orcalcium carbonate, chemical formula CaCO3, is formed fromwater, H2O, andcarbon dioxide, CO2, dissolved in the water. The carbon dioxide provides two of the oxygen atoms in the calcite. Thecalciummust rob the third from the water. The isotope ratio in the calcite is therefore the same, after compensation, as the ratio in the water from which the microorganisms of a given layer extracted the material of the shell. The microorganism most frequently referenced isforaminifera.[citation needed]Marine oxygen isotope recordTheisotopicrecord is based on theratio of two oxygenisotopes, oxygen-16 (16O) and oxygen-18 (18O), which is determined on calcium carbonate from shells of microfossils that accumulated year by year on the seafloor. The ratio depends on two factors, the temperature and the isotopic composition of theseawaterfrom which the organism secreted its shell. Shells secreted from colder water contain more oxygen-18 relative to oxygen-16 than do shells secreted from warmer water. The isotopic composition of the oceans has proved to be related to the storage of water in large ice sheets on land. Because molecules of oxygen-18 evaporate less readily and condense more readily, an air mass with oceanic water vapour becomes depleted in the heavier isotope (oxygen-18) as the air mass is cooled and loses water by precipitation. When moisture condenses and falls as snow, its isotopic composition is also dependent on the temperature of the air. Snow falling on a large ice sheet becomes isotopically lighter (i.e., has less oxygen-18) as one goes higher on the glacier surface where it is both colder and farther from the moisture source.

Incompatible and Compatible Elements Transition elements - Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn All compatible, no huge differences Low abundances in felsic or intermediate

Liquid Line of DescentOverall Conclusions and Andesite Petrogenetic Model: IIMost island arc lavas are extremely phenocryst rich; theirbulk composition then do not likely represent true liquidcompositions.Smooth Harker diagrams for all major elements. Impliescommon liquid-line of descent driven by fractionalcrystallization of SiO2-poor and FeO-rich such as Timagnetiteand amphibole.Sr-enrichment from seawater alteration of hydratedbasaltic oceanic crust and Pb-enrichment from terrigenoussediments (1-3%).Volatiles from descending slab are liberated into overlyingmantle wedge. Initiates partial melting yielding water-bearingbasalts. Basalts are enriched in the subduction component(LIL and LREE, Sr, Pb enriched). The basalts transit mantlewedge and in older arcs likely pond at MOHO, where theymay melt the lower crust and differentiate by fractionalcrystallization. More evolved magmas (lower density) riseinto mid-crust and periodically erupt.Some evidence for repeated basalt injections into midcrustalstorage zones in the form of zoned crystals, variableFe-Ti oxide-derived temperatures, and textures of maficinclusions.