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New Melones Dam, West Belt, Calaveras Co., California, USAi
Regional Level Types
New Melones DamDam
West Belt- not defined -
Calaveras Co.County
CaliforniaState
USACountry

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Key
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Latitude & Longitude (WGS84):
37° 56' 58'' North , 120° 31' 27'' West
Latitude & Longitude (decimal):
Locality type:
Nearest Settlements:
PlacePopulationDistance
Tuttletown668 (2011)7.3km
Jamestown3,433 (2011)8.9km
Copperopolis3,671 (2011)10.9km
Chinese Camp126 (2011)11.8km
Sonora4,818 (2017)13.0km


An occurrence located in the SW¼SW¼ sec. 11, T1N, R13E, MDM, at the spillway of the dam, about 11.4 km ESE of Copperopolis.

Partial Facsimile of the excellent Mineralogical Record article by:
Demetrius Pohl, Renald Guillemette, James Shigley and Gail Dunning


In the fall of 1981, very fine Ferroaxinite specimens were collected
from the spillway adjacent to New Melones Lake near Copperopolis in
Calaveras county. Since its discovery, this locality has produced some
of the finest ferroaxinite specimens ever found in North America.





INTRODUCTION
At the new Melones Lake spillway area, ferroaxinite was first noticed in the 1970's by engineers during dam construction, when it was observed during overburden removal. The locality has remained dormant since the completion of the dam and access to the site is restricted because the area comprises part of the New Melones Dam installations which are under the jurisdiction of the U.S. Bureau of Reclamation.


GEOLOGICAL SETTING



Regional Geology:
The spillway of New Melones Lake has been excavated in rocks of the western Sierra Nevada metamorphic belt. This belt forms part of the western limb of a north west-trending faulted synclinorium (a broad regional syncline on which are superimposed minor folds), the axial part of which is occupied by the granitic rocks of the Sierra Nevada batholith. Rocks in this belt consist of alternating metamorphosed volcanic and sedimentary units which are considered to be part of an early Mesozoic island-arc system and the underlying oceanic crust. In the New Melones Lake area the rocks have been divided into three major units: a basement of melange and serpentinite matrix melanges, an overlying island-arc volcanic unit, and finally an upper unit of slate and graywacke designated as the Mariposa formation. The melange and lower parts of the volcanic succession have been faulted into the overlying Upper Jurassic Mariposa formations.

Local Geology:
Although the regional geologic fabric trends northwest, the rocks exposed in the spillway show contacts oriented from west to north-west. The main lithologic units are massive grey-green gabbros with abundant diabase dikes, fine grained and in some places vesicular basalts and volcanics including both tuff and pillow lavas, all of which have been altered to greenstone. These are considered to be part of the Peno Blanco volcanics. Meta-argillites, melange rocks and serpentinites comprise a minor part of the stratigraphic section. All of these rocks have undergone greenshist facies metamorphism and locally show pervasive alteration to fine grained albite-epidote-quartz assemblages. In spite of the extensive alteration, deformation and faulting of the rocks, many original igneous and sedimentary features have been preserved. A shear foliation or shistosity is developed in the rocks only locally in the vicinity of the faults.

Rocks in the spillway are cut by many north-west trending faults and shear zones which dip either steeply to the northeast or gently to the southwest. Extension fractures or tension gashes are abundant in the metagabbro and metabasalt units in the spillway walls, but are absent in the less competent metasediments and serpentinite. These gash veins generally occur as sub-horizontal, en echelon, left-lateral groups dipping gently to the west. Some of these veins form ladder-like sets; these being confined to to basic dikes which intrude the metagabbro and metavolcanics. The length of the gash veins varies from 10 centimeters to 10 meters with a thickness of 2-30 cm. In plan view they are lens shaped. In some cases individuals are stacked so closely as to coalesce, as in areas 1 and 2 (fig. 1), with resultant thicknesses up to one meter. Most veins are undeformed and not offset by later events, and consequently record one of the last tectonic episodes in the area. It is in these gash veins that the ferroaxinite and other minerals of interest occur in the spillway. Ferroaxinite is confined to the veins, in contrast to the other minerals which also occur disseminated in the wall-rock. In general, most of the veins are completely filled with massive ferroaxinite and only rarely will a cavity be encountered. To date only five major veins which contain central cavities with free growing ferroaxinite and associated minerals have been found. These locations, numbered as areas 1 to 5, are shown on figure 1. Mineralogical data presented in this paper were collected from an examination of specimens collected at these localities.

In summary, the rocks found in the New Melones lake area consist of a structurally complex assortment of ancient oceanic crust, melanges and sheets of ultramafic rocks that evidently were deformed prior to the formation of the island arc. This entire assemblage has undergone additional tectonic shuffling during the late Jurassic, both prior to and during the Nevadan Orogeny, when the entire terrane was strongly folded and cleaved. The last event, around 150 million years ago, was most probably responsible for the generation of the gash veins and their spectacular ferroaxinite mineralization.




MINERALOGY



Ferroaxinite
Although a large number of tension veins exposed in the spillway contain massive, coarsely crystalline ferroaxinite, to date only a few of them have produced well formed euhedral crystals. Locations of the major veins with crystal-lined pockets are shown on figure 1. Ferroaxinite displays slightly differing color, morphology and paragenesis, depending on the location of the vein. The morphology of the crystals is typical of axinite, the crystals being thin and tabular with a wedge-like habit. Both single crystals and complex groups have been found. While its crystal habit is not unusual, the size, color, luster and general quality of this ferroaxinite are exceptional. Individual crystals can range up to 8 cm in longest dimension and parallel growth aggregated up to 12 cm. While much of the ferroaxinite is cloudy or opaque, thin fragments, small crystals and even many of the large ones are transparent and gemmy, particularly at their tips. All ferroaxinite from the spillway is violet or clove brown. Crystals from areas 1, 2, and 4 exhibit strong selective absorption as they are rotated in front of a light source; their color changing from pale violet-brown to deep reddish-violet. Veins from area 1 have produced both the most spectacular and largest number of ferroaxinite to date. This ferroaxinite generally occurs as fans and rosettes of crystals, box-works of bladed crystals, or single, parallel growth crystals implanted on either massive, granular ferroaxinite or a matrix of small epidote, actinolite and albite crystals. While many of the crystals have razor-sharp edges, some show small serrations which upon close examination are found to be multiple terminations or possibly growth hillocks.



ASSOCIATED MINERALS

Actinolite
Actinolite commonly occurs as white to very pale green flexible fibers in areas 1 and 3 as well as well as many of the smaller veins. In area 1, fibrous crystals to 1 cm cover areas up to 60 X 30 cm and occur with albite to form attractive plates. It has also been found in one vein of area 3 as flexible, long-fibered (up to 15 cm) parallel aggregates.





Albite
Albite is found in all major open cavities to date. It occurs as translucent white to water-clear, euhedral, striated, twinned crystals ranging from microscopic to almost 2 cm in diameter. Chlorite phantoms are sometimes seen within specimens from areas 3 and 5. Microprobe analysis show that the albites contain less than one percent anorthite and orthoclase components.



Calcite
Calcite most commonly occurs as colorless, translucent to transparent very coarsly-crystalline anhedral vein fillings. In areas 2 and 5 it is also found as large, thin, platy crystals forming a box-work among other minerals in the cavities. Several thin, hexagonal plates up to 3 cm across have been found as floaters in granular chlorite. Small, well-defined, blocky crystals are sometimes found growing on platy calcite and directly on ferroaxinite from areas 1 and 2.


Chalcopyrite
Chalcopyrite has been found only at a small, unreferenced vein area across the spillway from area 1. The crystals occur as crude polyhedra up to 6 mm in diameter within chlorite, and as thin veinlets in the vein core and in the surrounding rock.


Chlorite
Chlorite occurs as thick, loose, clay-like fillings within the open vein cavities of areas 3 and 5, as well as in many minor veins throughout the spillway. It typically forms attractive phantoms within quartz and albite. Chlorite inclusions within, and coatings of chlorite on quartz and ferroaxinite can give these crystals a dark grey-green, corroded appearance.



Epidote
Epidote has been found as small euhedral crystals in areas 1, 3 and 4 and in many of the smaller open cavities, and as granular and fibrous masses in the veins. The crystals rarely exceed 10 mm in length, form parallel groups and crusts, and display the typical olive-green color.


Palygorskite
This fibrous, clay-like mineral has only been found in area 1. It occurs as pale brown to orange gel-like or fibrous cavity fillings which completely envelope the central crystals in this area.

Pyrite
Small (less than 1 cm) cubes of pyrite have been found only in area 2, as an early-formed vein and wall-rock phase. It also occurs as disseminated crystals in the wall rocks of the spillway.


Quartz
Quartz has been found in all major veins except those of area 1. It generally occurs as colorless, translucent to transparent crystals up to 10 cm or more in length, though the average is 2 to 5 cm. Some of the crystals have patches and phantom inclusions of chlorite and more rarely ferroaxinite, albite, epidote and actinolite.


Smectite
A pale greyish yellow smectite-group mineral - most probably montmorillonite - fills interstices between ferroaxinite and albite crystals in area 2. It also occurs as a coating between calcite plates and possibly as inclusions in calcite.






PARAGENESIS


Each of the major vein pockets from areas 1 to 5 have somewhat different mineral assemblages and the paragenesis of each pocket is shown in figure 18. The absence of particular minerals from pocket to pocket is especially striking. There are also small but significant chemical differences between the pockets as shown by variations in ferroaxinite color and composition, differences in clay mineralogy, and the color of epidote.










Regions containing this locality

Pacific OceanOcean
North America PlateTectonic Plate

Select Mineral List Type

Standard Detailed Strunz Dana Chemical Elements

Mineral List

Mineral list contains entries from the region specified including sub-localities

21 valid minerals.

Detailed Mineral List:

Actinolite
Formula: ☐{Ca2}{Mg4.5-2.5Fe0.5-2.5}(Si8O22)(OH)2
Habit: flexible fibers; fibrous crystals
Colour: white to palegren
Reference: Pohl, D. et al. (1982): Ferroaxinite from New Melones Lake, Calaveras County, California, a remarkable new locality. Mineralogical Record 13 (5), 293-302
Aegirine
Formula: NaFe3+Si2O6
Reference: Albino, G. V. (1995). Sodium metasomatism along the Melones fault zone, Sierra Nevada foothills, California, USA. Mineralogical Magazine, 59(3), 383-399.
Albite
Formula: Na(AlSi3O8)
Habit: euhedral twinned crystals - microscopic up to 2 cm
Colour: colorless
Reference: Pohl, D. et al. (1982): Ferroaxinite from New Melones Lake, Calaveras County, California, a remarkable new locality. Mineralogical Record 13 (5), 293-302
Albite var: Cleavelandite
Formula: Na(AlSi3O8)
Reference: Albino, G. V. (1995). Sodium metasomatism along the Melones fault zone, Sierra Nevada foothills, California, USA. Mineralogical Magazine, 59(3), 383-399.
'Albite-Anorthite Series'
Reference: Albino, G. V. (1995). Sodium metasomatism along the Melones fault zone, Sierra Nevada foothills, California, USA. Mineralogical Magazine, 59(3), 383-399.
'Amphibole Supergroup'
Formula: AX2Z5((Si,Al,Ti)8O22)(OH,F,Cl,O)2
Reference: Albino, G. V. (1995). Sodium metasomatism along the Melones fault zone, Sierra Nevada foothills, California, USA. Mineralogical Magazine, 59(3), 383-399.
Analcime
Formula: Na(AlSi2O6) · H2O
Reference: Albino, G. V. (1995). Sodium metasomatism along the Melones fault zone, Sierra Nevada foothills, California, USA. Mineralogical Magazine, 59(3), 383-399.
Axinite-(Fe)
Formula: Ca2Fe2+Al2BSi4O15OH
Reference: Pohl, D. et al (1982): Ferroaxinite from New Melones Lake, Calaveras County, California, a remarkable new locality. Mineralogical Record 13 (5), 293-302
Calcite
Formula: CaCO3
Habit: anhedral vein fillings; blocky crystals
Reference: Pohl, D. et al. (1982): Ferroaxinite from New Melones Lake, Calaveras County, California, a remarkable new locality. Mineralogical Record 13 (5), 293-302
Chalcopyrite
Formula: CuFeS2
Reference: Pohl, D. et al. (1982): Ferroaxinite from New Melones Lake, Calaveras County, California, a remarkable new locality. Mineralogical Record 13 (5), 293-302
'Chlorite Group'
Habit: veriform pseudohexagonal
Reference: Pohl, D. et al. (1982): Ferroaxinite from New Melones Lake, Calaveras County, California, a remarkable new locality. Mineralogical Record 13 (5), 293-302
Clinochlore
Formula: Mg5Al(AlSi3O10)(OH)8
Epidote
Formula: {Ca2}{Al2Fe3+}(Si2O7)(SiO4)O(OH)
Reference: Pohl, D. et al. (1982): Ferroaxinite from New Melones Lake, Calaveras County, California, a remarkable new locality. Mineralogical Record 13 (5), 293-302
Gold
Formula: Au
Reference: U.S. Geological Survey, 2005, Mineral Resources Data System: U.S. Geological Survey, Reston, Virginia.
Hematite
Formula: Fe2O3
Reference: Albino, G. V. (1995). Sodium metasomatism along the Melones fault zone, Sierra Nevada foothills, California, USA. Mineralogical Magazine, 59(3), 383-399.
Magnetite
Formula: Fe2+Fe3+2O4
Reference: Albino, G. V. (1995). Sodium metasomatism along the Melones fault zone, Sierra Nevada foothills, California, USA. Mineralogical Magazine, 59(3), 383-399.
Marialite
Formula: Na4Al3Si9O24Cl
Reference: Albino, G. V. (1995). Sodium metasomatism along the Melones fault zone, Sierra Nevada foothills, California, USA. Mineralogical Magazine, 59(3), 383-399.
Muscovite
Formula: KAl2(AlSi3O10)(OH)2
Reference: Albino, G. V. (1995). Sodium metasomatism along the Melones fault zone, Sierra Nevada foothills, California, USA. Mineralogical Magazine, 59(3), 383-399.
Muscovite var: Sericite
Formula: KAl2(AlSi3O10)(OH)2
Reference: Albino, G. V. (1995). Sodium metasomatism along the Melones fault zone, Sierra Nevada foothills, California, USA. Mineralogical Magazine, 59(3), 383-399.
'Orthochrysotile'
Palygorskite
Formula: (Mg,Al)5(Si,Al)8O20(OH)2 · 8H2O
Habit: gel-like
Colour: palebrown to orange
Reference: Pohl, D. et al. (1982): Ferroaxinite from New Melones Lake, Calaveras County, California, a remarkable new locality. Mineralogical Record 13 (5), 293-302
Paragonite
Formula: NaAl2(AlSi3O10)(OH)2
Reference: Albino, G. V. (1995). Sodium metasomatism along the Melones fault zone, Sierra Nevada foothills, California, USA. Mineralogical Magazine, 59(3), 383-399.
Pyrite
Formula: FeS2
Reference: The Mineralogical Record, Vol. 13, #5, pages 293-302.
'Pyroxene Group'
Reference: Albino, G. V. (1995). Sodium metasomatism along the Melones fault zone, Sierra Nevada foothills, California, USA. Mineralogical Magazine, 59(3), 383-399.
Quartz
Formula: SiO2
Reference: Pohl, D. et al. (1982): Ferroaxinite from New Melones Lake, Calaveras County, California, a remarkable new locality. Mineralogical Record 13 (5), 293-302
Riebeckite
Formula: ◻[Na2][Fe2+3Fe3+2]Si8O22(OH)2
Reference: Albino, G. V. (1995). Sodium metasomatism along the Melones fault zone, Sierra Nevada foothills, California, USA. Mineralogical Magazine, 59(3), 383-399.
Rutile
Formula: TiO2
Reference: Albino, G. V. (1995). Sodium metasomatism along the Melones fault zone, Sierra Nevada foothills, California, USA. Mineralogical Magazine, 59(3), 383-399.
'Scapolite'
Reference: Albino, G. V. (1995). Sodium metasomatism along the Melones fault zone, Sierra Nevada foothills, California, USA. Mineralogical Magazine, 59(3), 383-399.
'Smectite Group'
Formula: A0.3D2-3[T4O10]Z2 · nH2O
Reference: Pohl, D. et al. (1982): Ferroaxinite from New Melones Lake, Calaveras County, California, a remarkable new locality. Mineralogical Record 13 (5), 293-302
Titanite
Formula: CaTi(SiO4)O
Reference: Albino, G. V. (1995). Sodium metasomatism along the Melones fault zone, Sierra Nevada foothills, California, USA. Mineralogical Magazine, 59(3), 383-399.

List of minerals arranged by Strunz 10th Edition classification

Group 1 - Elements
Gold1.AA.05Au
Group 2 - Sulphides and Sulfosalts
Chalcopyrite2.CB.10aCuFeS2
Pyrite2.EB.05aFeS2
Group 4 - Oxides and Hydroxides
Hematite4.CB.05Fe2O3
Magnetite4.BB.05Fe2+Fe3+2O4
Quartz4.DA.05SiO2
Rutile4.DB.05TiO2
Group 5 - Nitrates and Carbonates
Calcite5.AB.05CaCO3
Group 9 - Silicates
Actinolite9.DE.10☐{Ca2}{Mg4.5-2.5Fe0.5-2.5}(Si8O22)(OH)2
Aegirine9.DA.25NaFe3+Si2O6
Albite9.FA.35Na(AlSi3O8)
var: Cleavelandite9.FA.35Na(AlSi3O8)
Analcime9.GB.05Na(AlSi2O6) · H2O
Axinite-(Fe)9.BD.20Ca2Fe2+Al2BSi4O15OH
Clinochlore9.EC.55Mg5Al(AlSi3O10)(OH)8
Epidote9.BG.05a{Ca2}{Al2Fe3+}(Si2O7)(SiO4)O(OH)
Marialite9.FB.15Na4Al3Si9O24Cl
Muscovite9.EC.15KAl2(AlSi3O10)(OH)2
var: Sericite9.EC.15KAl2(AlSi3O10)(OH)2
Palygorskite9.EE.20(Mg,Al)5(Si,Al)8O20(OH)2 · 8H2O
Paragonite9.EC.15NaAl2(AlSi3O10)(OH)2
Riebeckite9.DE.25◻[Na2][Fe2+3Fe3+2]Si8O22(OH)2
Titanite9.AG.15CaTi(SiO4)O
Unclassified Minerals, Rocks, etc.
'Albite-Anorthite Series'-
'Amphibole Supergroup'-AX2Z5((Si,Al,Ti)8O22)(OH,F,Cl,O)2
'Chlorite Group'-
'Orthochrysotile'-
'Pyroxene Group'-
'Scapolite'-
'Smectite Group'-A0.3D2-3[T4O10]Z2 · nH2O

List of minerals arranged by Dana 8th Edition classification

Group 1 - NATIVE ELEMENTS AND ALLOYS
Metals, other than the Platinum Group
Gold1.1.1.1Au
Group 2 - SULFIDES
AmBnXp, with (m+n):p = 1:1
Chalcopyrite2.9.1.1CuFeS2
AmBnXp, with (m+n):p = 1:2
Pyrite2.12.1.1FeS2
Group 4 - SIMPLE OXIDES
A2X3
Hematite4.3.1.2Fe2O3
AX2
Rutile4.4.1.1TiO2
Group 7 - MULTIPLE OXIDES
AB2X4
Magnetite7.2.2.3Fe2+Fe3+2O4
Group 14 - ANHYDROUS NORMAL CARBONATES
A(XO3)
Calcite14.1.1.1CaCO3
Group 52 - NESOSILICATES Insular SiO4 Groups and O,OH,F,H2O
Insular SiO4 Groups and O, OH, F, and H2O with cations in [6] and/or >[6] coordination
Titanite52.4.3.1CaTi(SiO4)O
Group 56 - SOROSILICATES Si2O7 Groups, With Additional O, OH, F and H2O
Si2O7 Groups and O, OH, F, and H2O with cations in [4] and/or >[4] coordination
Axinite-(Fe)56.2.2.1Ca2Fe2+Al2BSi4O15OH
Group 58 - SOROSILICATES Insular, Mixed, Single, and Larger Tetrahedral Groups
Insular, Mixed, Single, and Larger Tetrahedral Groups with cations in [6] and higher coordination; single and double groups (n = 1, 2)
Epidote58.2.1a.7{Ca2}{Al2Fe3+}(Si2O7)(SiO4)O(OH)
Group 65 - INOSILICATES Single-Width,Unbranched Chains,(W=1)
Single-Width Unbranched Chains, W=1 with chains P=2
Aegirine65.1.3c.2NaFe3+Si2O6
Group 71 - PHYLLOSILICATES Sheets of Six-Membered Rings
Sheets of 6-membered rings with 2:1 layers
Muscovite71.2.2a.1KAl2(AlSi3O10)(OH)2
Paragonite71.2.2a.2NaAl2(AlSi3O10)(OH)2
Sheets of 6-membered rings interlayered 1:1, 2:1, and octahedra
Clinochlore71.4.1.4Mg5Al(AlSi3O10)(OH)8
Group 74 - PHYLLOSILICATES Modulated Layers
Modulated Layers with joined strips
Palygorskite74.3.1a.1(Mg,Al)5(Si,Al)8O20(OH)2 · 8H2O
Group 75 - TECTOSILICATES Si Tetrahedral Frameworks
Si Tetrahedral Frameworks - SiO2 with [4] coordinated Si
Quartz75.1.3.1SiO2
Group 76 - TECTOSILICATES Al-Si Framework
Al-Si Framework with Al-Si frameworks
Albite76.1.3.1Na(AlSi3O8)
Al-Si Framework with other Be/Al/Si frameworks
Marialite76.3.1.1Na4Al3Si9O24Cl
Group 77 - TECTOSILICATES Zeolites
Zeolite group - True zeolites
Analcime77.1.1.1Na(AlSi2O6) · H2O
Unclassified Minerals, Mixtures, etc.
Actinolite-☐{Ca2}{Mg4.5-2.5Fe0.5-2.5}(Si8O22)(OH)2
Albite
var: Cleavelandite
-Na(AlSi3O8)
'Albite-Anorthite Series'-
'Amphibole Supergroup'-AX2Z5((Si,Al,Ti)8O22)(OH,F,Cl,O)2
'Chlorite Group'-
Muscovite
var: Sericite
-KAl2(AlSi3O10)(OH)2
'Orthochrysotile'-
'Pyroxene Group'-
Riebeckite-◻[Na2][Fe2+3Fe3+2]Si8O22(OH)2
'Scapolite'-
'Smectite Group'-A0.3D2-3[T4O10]Z2 · nH2O

List of minerals for each chemical element

HHydrogen
H Epidote{Ca2}{Al2Fe3+}(Si2O7)(SiO4)O(OH)
H Axinite-(Fe)Ca2Fe2+Al2BSi4O15OH
H Actinolite☐{Ca2}{Mg4.5-2.5Fe0.5-2.5}(Si8O22)(OH)2
H Palygorskite(Mg,Al)5(Si,Al)8O20(OH)2 · 8H2O
H ClinochloreMg5Al(AlSi3O10)(OH)8
H Smectite GroupA0.3D2-3[T4O10]Z2 · nH2O
H ParagoniteNaAl2(AlSi3O10)(OH)2
H Amphibole SupergroupAX2Z5((Si,Al,Ti)8O22)(OH,F,Cl,O)2
H Muscovite (var: Sericite)KAl2(AlSi3O10)(OH)2
H AnalcimeNa(AlSi2O6) · H2O
H Riebeckite◻[Na2][Fe32+Fe23+]Si8O22(OH)2
H MuscoviteKAl2(AlSi3O10)(OH)2
BBoron
B Axinite-(Fe)Ca2Fe2+Al2BSi4O15OH
CCarbon
C CalciteCaCO3
OOxygen
O Albite (var: Cleavelandite)Na(AlSi3O8)
O Epidote{Ca2}{Al2Fe3+}(Si2O7)(SiO4)O(OH)
O Axinite-(Fe)Ca2Fe2+Al2BSi4O15OH
O Actinolite☐{Ca2}{Mg4.5-2.5Fe0.5-2.5}(Si8O22)(OH)2
O AlbiteNa(AlSi3O8)
O CalciteCaCO3
O Palygorskite(Mg,Al)5(Si,Al)8O20(OH)2 · 8H2O
O QuartzSiO2
O ClinochloreMg5Al(AlSi3O10)(OH)8
O Smectite GroupA0.3D2-3[T4O10]Z2 · nH2O
O TitaniteCaTi(SiO4)O
O RutileTiO2
O ParagoniteNaAl2(AlSi3O10)(OH)2
O MagnetiteFe2+Fe23+O4
O Amphibole SupergroupAX2Z5((Si,Al,Ti)8O22)(OH,F,Cl,O)2
O Muscovite (var: Sericite)KAl2(AlSi3O10)(OH)2
O HematiteFe2O3
O AegirineNaFe3+Si2O6
O AnalcimeNa(AlSi2O6) · H2O
O Riebeckite◻[Na2][Fe32+Fe23+]Si8O22(OH)2
O MarialiteNa4Al3Si9O24Cl
O MuscoviteKAl2(AlSi3O10)(OH)2
FFluorine
F Amphibole SupergroupAX2Z5((Si,Al,Ti)8O22)(OH,F,Cl,O)2
NaSodium
Na Albite (var: Cleavelandite)Na(AlSi3O8)
Na AlbiteNa(AlSi3O8)
Na ParagoniteNaAl2(AlSi3O10)(OH)2
Na AegirineNaFe3+Si2O6
Na AnalcimeNa(AlSi2O6) · H2O
Na Riebeckite◻[Na2][Fe32+Fe23+]Si8O22(OH)2
Na MarialiteNa4Al3Si9O24Cl
MgMagnesium
Mg Actinolite☐{Ca2}{Mg4.5-2.5Fe0.5-2.5}(Si8O22)(OH)2
Mg Palygorskite(Mg,Al)5(Si,Al)8O20(OH)2 · 8H2O
Mg ClinochloreMg5Al(AlSi3O10)(OH)8
AlAluminium
Al Albite (var: Cleavelandite)Na(AlSi3O8)
Al Epidote{Ca2}{Al2Fe3+}(Si2O7)(SiO4)O(OH)
Al Axinite-(Fe)Ca2Fe2+Al2BSi4O15OH
Al AlbiteNa(AlSi3O8)
Al Palygorskite(Mg,Al)5(Si,Al)8O20(OH)2 · 8H2O
Al ClinochloreMg5Al(AlSi3O10)(OH)8
Al ParagoniteNaAl2(AlSi3O10)(OH)2
Al Amphibole SupergroupAX2Z5((Si,Al,Ti)8O22)(OH,F,Cl,O)2
Al Muscovite (var: Sericite)KAl2(AlSi3O10)(OH)2
Al AnalcimeNa(AlSi2O6) · H2O
Al MarialiteNa4Al3Si9O24Cl
Al MuscoviteKAl2(AlSi3O10)(OH)2
SiSilicon
Si Albite (var: Cleavelandite)Na(AlSi3O8)
Si Epidote{Ca2}{Al2Fe3+}(Si2O7)(SiO4)O(OH)
Si Axinite-(Fe)Ca2Fe2+Al2BSi4O15OH
Si Actinolite☐{Ca2}{Mg4.5-2.5Fe0.5-2.5}(Si8O22)(OH)2
Si AlbiteNa(AlSi3O8)
Si Palygorskite(Mg,Al)5(Si,Al)8O20(OH)2 · 8H2O
Si QuartzSiO2
Si ClinochloreMg5Al(AlSi3O10)(OH)8
Si TitaniteCaTi(SiO4)O
Si ParagoniteNaAl2(AlSi3O10)(OH)2
Si Amphibole SupergroupAX2Z5((Si,Al,Ti)8O22)(OH,F,Cl,O)2
Si Muscovite (var: Sericite)KAl2(AlSi3O10)(OH)2
Si AegirineNaFe3+Si2O6
Si AnalcimeNa(AlSi2O6) · H2O
Si Riebeckite◻[Na2][Fe32+Fe23+]Si8O22(OH)2
Si MarialiteNa4Al3Si9O24Cl
Si MuscoviteKAl2(AlSi3O10)(OH)2
SSulfur
S PyriteFeS2
S ChalcopyriteCuFeS2
ClChlorine
Cl Amphibole SupergroupAX2Z5((Si,Al,Ti)8O22)(OH,F,Cl,O)2
Cl MarialiteNa4Al3Si9O24Cl
KPotassium
K Muscovite (var: Sericite)KAl2(AlSi3O10)(OH)2
K MuscoviteKAl2(AlSi3O10)(OH)2
CaCalcium
Ca Epidote{Ca2}{Al2Fe3+}(Si2O7)(SiO4)O(OH)
Ca Axinite-(Fe)Ca2Fe2+Al2BSi4O15OH
Ca Actinolite☐{Ca2}{Mg4.5-2.5Fe0.5-2.5}(Si8O22)(OH)2
Ca CalciteCaCO3
Ca TitaniteCaTi(SiO4)O
TiTitanium
Ti TitaniteCaTi(SiO4)O
Ti RutileTiO2
Ti Amphibole SupergroupAX2Z5((Si,Al,Ti)8O22)(OH,F,Cl,O)2
FeIron
Fe Epidote{Ca2}{Al2Fe3+}(Si2O7)(SiO4)O(OH)
Fe Axinite-(Fe)Ca2Fe2+Al2BSi4O15OH
Fe Actinolite☐{Ca2}{Mg4.5-2.5Fe0.5-2.5}(Si8O22)(OH)2
Fe PyriteFeS2
Fe ChalcopyriteCuFeS2
Fe MagnetiteFe2+Fe23+O4
Fe HematiteFe2O3
Fe AegirineNaFe3+Si2O6
Fe Riebeckite◻[Na2][Fe32+Fe23+]Si8O22(OH)2
CuCopper
Cu ChalcopyriteCuFeS2
AuGold
Au GoldAu

Regional Geology

This geological map and associated information on rock units at or nearby to the coordinates given for this locality is based on relatively small scale geological maps provided by various national Geological Surveys. This does not necessarily represent the complete geology at this locality but it gives a background for the region in which it is found.

Click on geological units on the map for more information. Click here to view full-screen map on Macrostrat.org

Jurassic
145 - 201.3 Ma



ID: 2932359
Mesozoic volcanic rocks, unit 2 (Western Sierra Foothills and Western Klamath Mountains)

Age: Jurassic (145 - 201.3 Ma)

Stratigraphic Name: Copper Hill Volcanics; Gopher Ridge Volcanics; Logtown Ridge Formation; Mariposa Formation; Monte de Oro Formation; Oregon City Formation; Peaslee Creek Volcanics; Penon Blanco Formation; Brower Creek Volcanic Member; Smartville Complex

Description: Undivided Mesozoic volcanic and metavolcanic rocks. Andesite and rhyolite flow rocks, greenstone, volcanic breccia and other pyroclastic rocks; in part strongly metamorphosed. Includes volcanic rocks of Franciscan Complex: basaltic pillow lava, diabase, greenstone, and minor pyroclastic rocks.

Comments: Western Sierra Nevada and western Klamath Mountains. Mostly basaltic to andesitic breccias, flows, and tuffs, metamorphosed but with primary volcanic features generally recognizable. Minor associated sandstone and conglomerate. Largely or entirely of marine origin. Includes some rocks interpreted as ophiolites (Smartville complex) Original map source: Saucedo, G.J., Bedford, D.R., Raines, G.L., Miller, R.J., and Wentworth, C.M., 2000, GIS Data for the Geologic Map of California, California Department of Conservation, Division of Mines and Geology, CD-ROM 2000-07, scale 1:750,000.

Lithology: Major:{mafic volcanic}, Minor:{felsic volcanic}, Incidental:{chert, sandstone, conglomerate}

Reference: Horton, J.D., C.A. San Juan, and D.B. Stoeser. The State Geologic Map Compilation (SGMC) geodatabase of the conterminous United States. doi: 10.3133/ds1052. U.S. Geological Survey Data Series 1052. [133]

Jurassic - Triassic
145 - 251.902 Ma



ID: 3189515
Mesozoic sedimentary and volcanic rocks

Age: Mesozoic (145 - 251.902 Ma)

Lithology: Mudstone-carbonate-sandstone-conglomerate

Reference: Chorlton, L.B. Generalized geology of the world: bedrock domains and major faults in GIS format: a small-scale world geology map with an extended geological attribute database. doi: 10.4095/223767. Geological Survey of Canada, Open File 5529. [154]

Data and map coding provided by Macrostrat.org, used under Creative Commons Attribution 4.0 License

References

Sort by

Year (asc) Year (desc) Author (A-Z) Author (Z-A)
Lacroix, A. (1893-95) Mineralogie de la France et de ses colonies. Libraire Polytechnique, Baudry et Cie, Editeurs.
Goldschmidt, Victor (1913), Atlas der Krystallformen. Vol. 1, Carl Winters Universitatsbuchhandlung, Heidelburg.
Parker, R. L. (1954) Die Mineralfunde der Schweizer Alpen. Wepf and Co., Verlag, Basel.
Clark, L. D. (1964) Stratigraphy and structure of part of the western Sierra Nevada metamorphic belt, California. U.S. Geological Survey, Professional Paper 410, 70 pp.
Murdoch, J., and Webb, R. W. (1966) Minerals of California, Centennial Volume (1866-1966). Bulletin 189,California Division of Mines and Geology, 559 pp.
Weibel, M. (1966) A guide to the minerals of Switzerland. Interscience Publishers, London.
Turner, F. J. (1968) Metamorphic Petrology; Mineralogical and field aspects. McGraw Hill, New York.
Thompson, G., and Melson, W. G. (1970) Boron contents of serpentinites and metabasalts in the oceanic crust: Implications for the boron cycle in the ocean. Earth and Planet Science Letters: 8: 61-65.
Bateman, P.C., and Clark, L.D. (1974) Stratigraphic and structural setting of the Sierra Nevada batholith, California. Pacific Geology: 8: 78-79.
Cowen, D. S. (1975) Early Mesozoic tectonic evolution of the western Sierra Nevada, California. Geological Society of America, Bulletin: 86: 1329-1336.
Cassedane, J., Cassedane, J., and Estrada, N. (1977) Le gite d'axinite de Santa Rosa (municipe de Condeuba, Etat de Bahia, Bresil). Bulletin Soc. Fr. Mineral. Crystallogr.: 100: 191-197.
Morgan, B. A. and Stern, T. W. (1977) Chronology of tectonic and plutonic events in the western Sierra Nevada between Sonora and Mariposa, California (abstr.) Geological society of America, Abstracts with Programs, 9, 471-472.
Leake, B. E. (1978) Nomenclature of Amphiboles. American Mineralogist, 63, 1023-1052.
Schweikert, R. A. (1978) Triassic and Jurassic paleogeography of the Sierra Nevada and adjacent regions, California and western Nevada, In D. G. Howell, and K. A. McDougall, Eds., Mesozoic paleogeography of the western United States. Pacific section, Soc. Econ. Paleontologists and Mineralogists, Pacific coast paleogeography symposium 2, 361-384.
Lumpkin, G. R. and Ribbe, P. H. (1979) Chemistry and physical properties of axinites. American Mineralogist: 64: 636-645.
Pohl, D., Guillemette, R. & Shigley, J., Dunning, Gail (1982): Ferroaxinite from New Melones Lake, Calaveras County, California, a remarkable new locality. Mineralogical Record: 13(5): 293-302.
Albino, G. V. (1995). Sodium metasomatism along the Melones fault zone, Sierra Nevada foothills, California, USA. Mineralogical Magazine, 59(3), 383-399.

Mindat Articles

Ferroaxinite from New Melones Lake, Calaveras County, California by Jake Harper


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