scholarly journals Mineralogy and Genesis of the Kihabe Zn-Pb-V Prospect, Aha Hills, Northwest Botswana

Minerals ◽  
2020 ◽  
Vol 10 (8) ◽  
pp. 685
Author(s):  
Nicola Mondillo ◽  
Maria Boni ◽  
Giuseppina Balassone ◽  
Nigel Forrester ◽  
Francesco Putzolu ◽  
...  
Keyword(s):  
Late Cretaceous ◽  
Sulfide Minerals ◽  
Hydrothermal Systems ◽  
The Other ◽  
Fold Belt ◽  
Direct Precipitation ◽  
Hydrothermal Processes ◽  
Alteration Halo ◽  
Two Generations ◽  
Mixed Sulfide

The Kihabe Zn-Pb-V > (Cu-Ag-Ge) prospect is located at the boundary between Namibia and Botswana (Aha Hills, Ngamiland District) in a strongly deformed Proterozoic fold belt, corresponding to the NE extension of the Namibian Damara Orogen. The Kihabe prospect contains Zn-Pb resources of 14.4 million tonnes at 2.84% zinc equivalent, Ag resources of 3.3 million ounces, and notable V-Ge amounts, still not evaluated at a resource level. The ores are represented by a mixed sulfide–nonsulfide mineralization. Sulfide minerals consist mainly of sphalerite, galena and pyrite in a metamorphic quartzwacke. Among the nonsulfide assemblage, two styles of mineralization occur in the investigated samples: A first one, characterized by hydrothermal willemite and baileychlore, and a second one consisting of supergene smithsonite, cerussite, hemimorphite, Pb-phosphates, arsenates and vanadates. Willemite is present in two generations, which postdate sulfide emplacement and may also form at their expenses. These characteristics are similar to those observed in the willemite occurrences of the nearby Otavi Mountainland, which formed through hydrothermal processes, during the final stages of the Damara Orogeny. The formation of the Kihabe willemite is likely coeval. Baileychlore is characterized by textures indicating direct precipitation from solutions and dissolution–crystallization mechanisms. Both processes are typical of hydrothermal systems, thus suggesting a hydrothermal genesis for the Kihabe Zn-chlorite as well. Baileychlore could represent an alteration halo possibly associated either with the sulfide or with willemite mineralization. The other nonsulfide minerals, smithsonite, cerussite, various Pb-phosphates and vanadates, are clearly genetically associated with late phases of supergene alteration, which overprinted both the sulfide and the willemite- and baileychlore-bearing mineralizations. Supergene alteration probably occurred in this part of Botswana from the Late Cretaceous to the Miocene.

scholarly journals Trace Metal Distribution in Sulfide Minerals from Ultramafic-Hosted Hydrothermal Systems: Examples from the Kairei Vent Field, Central Indian Ridge

Minerals ◽  
2018 ◽  
Vol 8 (11) ◽  
pp. 526 ◽  
Author(s):  
Yejian Wang ◽  
Xiqiu Han ◽  
Sven Petersen ◽  
Matthias Frische ◽  
Zhongyan Qiu ◽  
...  
Keyword(s):  
Trace Elements ◽  
Trace Element ◽  
Massive Sulfide ◽  
Sulfide Minerals ◽  
Hydrothermal Systems ◽  
The Other ◽  
Central Indian Ridge ◽  
Sulfide Deposits ◽  
High Concentrations ◽  
Seafloor Massive Sulfide

The ultramafic-hosted Kairei vent field is located at 25°19′ S, 70°02′ E, towards the Northern end of segment 1 of the Central Indian Ridge (CIR-S1) at a water depth of ~2450 m. This study aims to investigate the distribution of trace elements among sulfide minerals of differing textures and to examine the possible factors controlling the trace element distribution in those minerals using LA-ICP-MS spot and line scan analyses. Our results show that there are distinct systematic differences in trace element distributions throughout the different minerals, as follows: (1) pyrite is divided into three types at Kairei, including early-stage euhedral pyrite (py-I), sub-euhedral pyrite (py-II), and colloform pyrite (py-III). Pyrite is generally enriched with Mo, Au, As, Tl, Mn, and U. Pyrite-I has high contents of Se, Te, Bi, and Ni when compared to the other types; py-II is enriched in Au relative to py-I and py-III, but poor in Ni; py-III is enriched in Mo, Pb, and U but is poor in Se, Te, Bi, and Au relative to py-I and py-II. Variations in the concentrations of Se, Te, and Bi in pyrite are most likely governed by the strong temperature gradient. There is generally a lower concentration of nickel than Co in pyrite, indicating that our samples precipitated at high temperatures, whereas the extreme Co enrichment is likely from a magmatic heat source combined with an influence of serpentinization reactions. (2) Chalcopyrite is characterized by high concentrations of Co, Se, and Te. The abundance of Se and Te in chalcopyrite over the other minerals is interpreted to have been caused by the high solubilities of Se and Te in the chalcopyrite lattice at high temperatures. The concentrations of Sb, As, and Au are relatively low in chalcopyrite from the Kairei vent field. (3) Sphalerite from Zn-rich chimneys is characterized by high concentrations of Sn, Co, Ga, Ge, Ag, Pb, Sb, As, and Cd, but is depleted in Se, Te, Bi, Mo, Au, Ni, Tl, Mn, Ba, V, and U in comparison with the other minerals. The high concentrations of Cd and Co are likely caused by the substitution of Cd2+ and Co2+ for Zn2+ in sphalerite. A high concentration of Pb accompanied by a high Ag concentration in sphalerite indicates that Ag occurs as Pb–Ag sulfosalts. Gold is generally low in sphalerite and strongly correlates with Pb, suggesting its presence in microinclusions of galena. The strong correlation of As with Ge in sphalerite from Kairei suggests that they might precipitate at medium temperatures and under moderately reduced conditions. (4) Bornite–digenite has very low concentrations of most trace elements, except for Co, Se, and Bi. Serpentinization in ultramafic-hosted hydrothermal systems might play an important role in Au enrichment in pyrite with low As contents. Compared to felsic-hosted seafloor massive sulfide deposits, sulfide minerals from ultramafic-hosted deposits show higher concentrations of Se and Te, but lower As, Sb, and Au concentrations, the latter often attributed to the contribution of magmatic volatiles. As with typical ultramafic-hosted seafloor massive sulfide deposits, Se enrichment in chalcopyrite from Kairei indicates that the primary factor that controls the Se enrichment is temperature-controlled mobility in vent fluids.

Common Lawà l'americaine

1966 ◽  
Vol 1 (4) ◽  
pp. 562-579 ◽  
Author(s):  
A. M. Apelbom
Keyword(s):  
Common Law ◽  
The Other ◽  
British Occupation ◽  
Other Hand ◽  
Two Generations ◽  
The Common ◽  
English Law ◽  
Considerable Body ◽  
Clear Line

Eighteen years after attaining independence Israel remains essentially a common law country. Introduced by the British Mandatory administration to supplement the Ottoman legislation in force at the time of the British occupation of Palestine, the common law has been retained by the Israeli legislator, so far as not modified or replaced by local legislation. But this common law, far from being residual only, also embraces a considerable body of interstitial law developed by two generations of judges, British, Palestinian and Israeli, in the process of applying and interpreting statute law—whether Ottoman, Mandatory or Israeli—according to common law methods. On the other hand the importation of common law institutions was neither wholesale nor systematic and in a number of fields no clear line of demarcation can be drawn between domestic and English law.

Multi-Aged Small Pterosaur Track Assemblage from the Upper Cretaceous of Korea

2021 ◽  
Author(s):  
Jongyun Jung ◽  
Min Huh ◽  
Koo-Geun Hwang ◽  
Hyun-Joo Kim ◽  
Byung-Do Choi ◽  
...  
Keyword(s):  
Late Cretaceous ◽  
Korean Peninsula ◽  
Upper Cretaceous ◽  
Global Distribution ◽  
The Other

Abstract The pterosaur is the earliest and largest powered flying vertebrate, even earlier and larger than the other extant archosaurian group, birds. However, evidence for this flying reptile, including the diversity of the small-sized pterosaur after the mid-Cretaceous, and their ecology, has remained elusive. Here we present numerous and dense pterosaur track assemblages from the Hwasun Seoyuri tracksite in the Upper Cretaceous Jangdong Formation of the Neungju Basin in Korea. The pterosaur track assemblage, assigned to Pteraichnus isp., consists of various sized, randomly oriented manus-dominated tracks with several pes claw marks. These features commonly indicate the semi-aquatic behavior and multi-age gregariousness of pterosaurs. The supposed trackmaker of pterosaur tracks would be the small-sized pterodactyloid that inhibited the Late Cretaceous Korean Peninsula, but that has not previously been reported. This ichnological evidence for the global distribution of small-sized pterosaurs could be interpreted to mean that the pterosaur fauna in the Late Cretaceous was more distributed and diverse than was previously known.

scholarly journals On Apogamy and the development of Sporangia upon fern prothalli

1898 ◽  
Vol 63 (389-400) ◽  
pp. 56-61
Keyword(s):  
Life History ◽  
Point Of View ◽  
The Other ◽  
Normal Life ◽  
Other Hand ◽  
General Importance ◽  
Two Generations ◽  
History Of ◽  
Alternation Of Generations

The two most important deviations from the normal life-history of ferns, apogamy and apospory, are of interest in themselves, but acquire a more general importance from the possibility that their study may throw light on the nature of alternation of generations in archegoniate plants. They have been considered from this point of view Pringsheim, and by those who, following him, regard the two generations as homologous with one another in the sense that the sporophyte arose by the gradual modification of individuals originally resemblin the sexual plant. Celakovsky and Bower, on the other hand, maintaint the view tha t the sporophyte, as an interpolated stage in the life-history arising by elaboration of the zygote, a few thallophytes.

scholarly journals Tectonic influence on axial-transverse sediment routing in the Denver Basin

2022 ◽  
Author(s):  
Glenn R. Sharman ◽  
Daniel F. Stockli ◽  
Peter Flaig ◽  
Robert G. Raynolds ◽  
Marieke Dechesne ◽  
...  
Keyword(s):  
Late Cretaceous ◽  
Detrital Zircon ◽  
Foreland Basin ◽  
The Other ◽  
Front Range ◽  
Denver Basin ◽  
Dispersal Patterns ◽  
Magmatic Arc ◽  
Sedimentary Sequences ◽  
Basin Fill

ABSTRACT Detrital zircon U-Pb and (U-Th)/He ages from latest Cretaceous–Eocene strata of the Denver Basin provide novel insights into evolving sediment sourcing, recycling, and dispersal patterns during deposition in an intracontinental foreland basin. In total, 2464 U-Pb and 78 (U-Th)/He analyses of detrital zircons from 21 sandstone samples are presented from outcrop and drill core in the proximal and distal portions of the Denver Basin. Upper Cretaceous samples that predate uplift of the southern Front Range during the Laramide orogeny (Pierre Shale, Fox Hills Sandstone, and Laramie Formation) contain prominent Late Cretaceous (84–77 Ma), Jurassic (169–163 Ma), and Proterozoic (1.69–1.68 Ga) U-Pb ages, along with less abundant Paleozoic through Archean zircon grain ages. These grain ages are consistent with sources in the western U.S. Cordillera, including the Mesozoic Cordilleran magmatic arc and Yavapai-Mazatzal basement, with lesser contributions of Grenville and Appalachian zircon recycled from older sedimentary sequences. Mesozoic zircon (U-Th)/He ages confirm Cordilleran sources and/or recycling from the Sevier orogenic hinterland. Five of the 11 samples from syn-Laramide basin fill (latest Cretaceous–Paleocene D1 Sequence) and all five samples from the overlying Eocene D2 Sequence are dominated by 1.1–1.05 Ga zircon ages that are interpreted to reflect local derivation from the ca. 1.1 Ga Pikes Peak batholith. Corresponding late Mesoproterozoic to early Neoproterozoic zircon (U-Th)/He ages are consistent with local sourcing from the southern Front Range that underwent limited Mesozoic–Cenozoic unroofing. The other six samples from the D1 Sequence yielded detrital zircon U-Pb ages similar to pre-Laramide units, with major U-Pb age peaks at ca. 1.7 and 1.4 Ga but lacking the 1.1 Ga age peak found in the other syn-Laramide samples. One of these samples yielded abundant Mesozoic and Paleozoic (U-Th)/He ages, including prominent Early and Late Cretaceous peaks. We propose that fill of the Denver Basin represents the interplay between locally derived sediment delivered by transverse drainages that emanated from the southern Front Range and a previously unrecognized, possibly extraregional, axial-fluvial system. Transverse alluvial-fluvial fans, preserved in proximal basin fill, record progressive unroofing of southern Front Range basement during D1 and D2 Sequence deposition. Deposits of the upper and lower D1 Sequence across the basin were derived from these fans that emanated from the southern Front Range. However, the finer-grained, middle portion of the D1 Sequence that spans the Cretaceous-Paleogene boundary was deposited by both transverse (proximal basin fill) and axial (distal basin fill) fluvial systems that exhibit contrasting provenance signatures. Although both tectonic and climatic controls likely influenced the stratigraphic development of the Denver Basin, the migration of locally derived fans toward and then away from the thrust front suggests that uplift of the southern Front Range may have peaked at approximately the Cretaceous-Paleogene boundary.

Patrick Maynard Stuart Blackett, Baron Blackett, of Chelsea, 18 November 1897 - 13 July 1974

1975 ◽  
Vol 21 ◽  
pp. 1-115 ◽  
Keyword(s):  
Church Of England ◽  
Large Family ◽  
The Other ◽  
Future Career ◽  
The Family ◽  
The Future ◽  
Two Generations ◽  
Indian Mutiny ◽  
The Church ◽  
Deep Interest

Patrick Maynard Stuart Blackett was born in Kensington, London, on 18 November 1897. His father, Arthur Stuart Blackett, was a stockbroker, although apparently not by inclination since his great interests were in literature and nature. Patrick was the only boy but had an elder and younger sister; one trained and practised as an architect in the 1920s, until she married, and the other became an industrial psychologist and then a psychoanalyst. For the previous two generations the family had been associated with the Church of England. Patrick’s grandfather had been Vicar of the church in Woburn Square (now demolished), and was the Vicar of St Andrew’s, Croydon, at the time of his death. He had twice married and Arthur Stuart was one of a large family, two of whom went into the Church, whilst another became a missionary in India. Patrick’s great-grandfather came from Hamsterley in Co. Durham of a farming family. He moved to London and his children were baptised in St Saviour’s Church, Southwark (now Southwark Cathedral). The future career and interests of Patrick seem to have more association with his maternal descent. His mother, Caroline Frances Maynard, was the daughter of Major Charles Maynard, R.A., who served in India at the time of the Indian Mutiny. William Maynard, a brother of Charles, was also associated with India as a tea planter. The source of Patrick’s deep interest in Indian affairs has this association; so does his early naval career and his continued absorption in military affairs—in addition to the army career of his grandfather there was an earlier tradition of naval service in the Maynard family.

Contact and the Alteration of Racial Attitudes in South Africa

1993 ◽  
Vol 23 (4) ◽  
pp. 204-211 ◽  
Author(s):  
Mandy Bradnum ◽  
Johann Nieuwoudt ◽  
Colin Tredoux
Keyword(s):  
South Africa ◽  
Racial Attitudes ◽  
The Other ◽  
English Speakers ◽  
Negative Attitudes ◽  
Consistent Finding ◽  
Segregated Schools ◽  
Two Generations ◽  
English Speaking ◽  
Normative Factors

Two generations of social psychologists have described a remarkably consistent pattern of racial attitudes in South Africa. Whites exhibit determinedly negative attitudes towards other ‘race’ groups (Afrikaans speakers more so than English speakers), and blacks, on the other hand, show a much lower degree of ethnocentrism, especially toward English-speaking whites. This ‘lop-sided colour bar’ is a consistent finding, both historically and across different attitudinal measures. We report results here that indicate that this pattern may be changing, in at least one part of the country. In addition, we examine the attitudes of school pupils in integrated and segregated schools, both in South Africa and in Zimbabwe, for evidence that inter-racial contact improves attitudinal dispositions. Our findings here offer little evidence in favour of the proposition: they appear instead to suggest the dependency of the effects of contact on cultural and normative factors.

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