Lava flow

V-Surficial, weakly coherent, alluvial deposits readily eroded by water. (Vj-<3 percent slope V2-<12 percent slope). I-Incompetent, or weakly coherent, bedrock such as shales and tuffs readily eroded by water and (or) prone to mass movement on steep slopes (li-<12 percent slope l2->12 percent slope). C-Competent, or strongly coherent, bedrock such as layered lava flow rocks and igneous intrusives not readily eroded by water, nor generally prone to mass movement except for rockslides and rockfalls from very steep slopes and cliffs (Ci-<12 percent slope). 

Some of the Kuroko deposits consist predominantly of pyrite containing a small amount of chalcopyrite. The ore deposits consisting predominantly of pyrite, either with an economical value of chalcopyrite or not, are called the Y sub-type deposits, which occur above dacite lava dome or lava flow, while copper-poor deposits occur mostly in pyroclastic rocks and are associated with a large amount of gypsum. The Matsumine deposit in the Hanaoka mine is typical of the Y sub-type. The Matsuki and Takadate deposits in the Matsuki mine are also classed as this sub-type (Kuroda, 1978). Many pyrite-rich ore bodies... 

The Hishikari Upper Andesites overlying the Hishikari Lower Andesites and the Shishimano Dacites consist of hypersthene-augite andesite lava flows and their pyroclastic rocks. 

Another recent study on historic, basaltic lava flows (1848 to 1977 AD) from Karthala volcano (Comores, Indian ocean) by Claude-Ivanad et al. (1998) reveals significant variations of the ( Ra)o/Ba ratios, correlated with Sr/ Sr ratios, which are explained by mantle source heterogeneities preserved by short transfer times of the magmas (a few centuries at most). 

Ra- Th disequilibria have also been measured in several prehistoric and historic lava flows from Hawaiian volcanoes (e.g., Cohen and O Nions 1993 Hemond et al. 1994 Sims et al. 1999 Pietruszka et al. 2001). All these authors assume that the ( Ra/ Th) ratios have not been affected by radioactive decay in the shallow open-system reservoirs of tholeiitic volcanoes like Kilauea, and this is supported by independent evidence for short magma residence times (e.g., < 200 years Pietruszka and Garcia 1999). 

Data on mineral s arates in present day volcanic rocks. Since every dating method (including the K-Ar or C systems) can be affected by several geochemical perturbations which may lead to erroneous ages, the best test for the °Th- U mineral isochrons consists in the analysis of presently erupted lavas or historic lavas of well known eruption dates. Rather surprisingly the data obtained on such samples are not so numerous (some examples are illustrated in Fig. 10). Early data showed that, in some cases, there were interlaboratory analytical discrepancies, especially in Th isotope ratios measured on mineral separates extracted from the same lava flows (this was the case for the 1971 lava from Mt. Etna and 1944 lava from Mt. Vesuvius Capaldi and Pece 1981 Hemond and Condomines 1985 Capaldi et al. 1985). This emphasizes the fact that °Th- U mineral analyses... 

Figure 24. Measured 6 Tla) vs. Th diagram used to infer the ages of lava flows from Mt. Etna in the age range 0 to 8 ka. The eurves labeled 0, 0.5, 1... ka correspond to isochron curves. The isochron 0 is defined by the 6 Tla)o-Th correlation observed in historical lava flows of the last two millennia (Condomines et al. 1995). Five samples of previously unknown ages are reported in this diagram (Condomines et al. 1995, and unpublished results).

Figure 12. Profiles of Th to Nb ratios for four Hawaiian soils developed on lava flows with ages ranging from 20 ka to 4100 ka (Kurtz et al. 2000). In these soils, Nb is assumed to be an irmnobile element. Variations of Th/Nb ratios, with lower values than those of basalt (greyed area) in the upper part of the profile and higher values in the lower part indieate an internal downward migration of Th in these fom weathering profiles. Cireles = 20 ka Laupahoehoe site, triangles = 150 ka Kohala site, squares = 1400 ka Molokai site, diamonds = 4100 ka Kauai site.

The most recent research results show that it is difficult to detect formerly liquid water on Mars. Pictures of what are assumed to be seafloors and riverbeds are no longer considered to be certain evidence that flowing water was always present in all the regions of Mars. Critical examination of some landscapes indicates that they were carved by lava flows and not by water. Only in the case of the edges of craters, and some river gullies, does it appear quite clear that they were formed by liquid water. However, at the time of writing, the Mars Reconnaissance Orbiter mission is only a few weeks old, so further important results (and perhaps surprises) on the surface and mineralogy of Mars can be expected (Baker, 2007). 

The basement complex for the Patagonian desert and arid northeastern Brazil is formed by metamorphosed Precambrian rocks. Landscapes are characterized by level erosion surfaces of different ages. The landscape is dissected by a large number of valleys. Large depressions are filled with marine and continental beds of sedimentary rocks. Rocks in the Andean system, that stretches the entire length of the west side of the continent, vary greatly. Many depressions are filled with sediments. In addition, many active volcanoes are responsible for periodic lava flows and the deposition of volcanic ash. East of the Andes, the land surface is level and slopes towards the Atlantic Ocean. Broad depressions contain saline or sodic soils. 

For the reasons outlined above, outcrops of workable obsidian are relatively few in number and are restricted to areas of geologically recent lava flows. Most sources are therefore reasonably well known, and, because of these constraints, identification of new sources in the eastern Mediterranean region becomes ever more unlikely. This makes the exercise of characterizing archaeological obsidians an attractive proposition, since, unlike potential clay sources for pottery provenance, the existence of completely unknown sources can be (cautiously) ignored. This is, of course, subject to the requirement noted above for more detailed geochemical characterization of existing sources. 

Figure 3.7 Spline interpolation of the chondrite normalized Ce/Yb ratio in recent lava flows of the Piton de la Fournaise volcano (Albarede and Tamagnan, 1988). The end derivatives are supposed to be zero.

Rhodes JM (1996) Geochemical stratigraphy of lava flows sampled by the Hawaii Scientific Drilling Project. JGeophysRes 101 11,729-11,746... 

We rented a house in the remote and desolate Kau district of the big island of Hawaii. It was an area of twisted lava flows of all ages. Kapukas were the only vegetation, islanded areas of ancient forest surrounded by frothy seas of hardened rock, which had killed all low-lying and less fortunate life. Slowly, nearly imperceptibly, Mauna Loa s gentle bulk rose up to fourteen thousand feet in the distance behind us. We were at approximately the twenty-five hundred foot... 

Figure 5.31 TTT diagram for a pyroxene of composition similar to C2 in figure 5.30. Curves a, b, c, and d cooling rates of a lava flow at increasing depths from surface (g) to 1 m inside the body ((i), based on calculations of Provost and Bottinga (1974). From Bu-seck et al. (1982). Reprinted with permission of The Mineralogical Society of America.

The second profile is Early Miocene in age and preserved beneath a leucitite lava flow dated at 17.1 0.2 Ma. The ferruginised upper part of the profile has been palaeomagnetically dated at 15 5Ma (McQueen et al. 2007). This profile also shows light REE depletion in the upper part, but not as marked as in the older profile (Fig. 3). There is also slight, relative enrichment in the heavy REE in the upper part of the profile. 

McQueen, K.G., Gonzalez, O.R., Roach, I.C.. PiLLAND, B.J., Dunlap, W.J., Smith M.L. 2007. Landscape and regoiith features related to Miocene leucitite lava flows, El Capitan northeast of Cobar, NSW, Australia. Australian Journal of Earth Sciences, 54, 1-17. 

Abstract Nash creek is the largest Zn-Pb deposit in the Tobique-Chaleurs Zone, and contains indicated and inferred resources of 7.8 Mt grading 2.72% Zn, 0.55% Pb and 18.26 g/t Ag and 1.2 Mt grading 2.66% Zn, 0.52% Pb and 18 g/t Ag, respectively. The deposit is hosted by Early Devonian bimodal volcanic and minor interlayered sedimentary rocks that were deposited in a trans-pressional rift. The host rocks sequence includes the Archibald Settlement Formation (rhyolite flows domes and related rocks), and the Sunnyside Formation (mafic lava flows and interlayered volcaniclastic and sedimentary rocks). 

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