Mineral Evolution Database

Created and maintained by the Mineral Evolution Project in partnership with RRUFF and mindat.

Mineral locality data provided by mindat.org

The Mineral Evolution database is currently under development.

The goal of this page is to present localities at which the mineral is found, and estimates of the oldest possible geologic age of the minerals at these localities.

Locality Name:
Nchisi Island (Chilwa Island; Shirwa Island), Zomba, Southern Region, Malawi

Oldest recorded age at locality: 145
Youngest recorded age at locality: 100

mindat Locality ID: 26432
mindat URL: http://www.mindat.org/loc-26432.html

Tectonic Settings:

Total number of sublocalities beneath "Nchisi Island (Chilwa Island; Shirwa Island), Zomba, Southern Region, Malawi": 0
Total number of bottom-level sublocalities: 0

Latitude: 15°19'54"S
Longitude: 35°36'7"E
Decimal Degree (lat, lon): -15.331666666667,35.601944444444

A	This mineral is Anthropogenic.
G	This mineral is directly dated.
B	This mineral is reported as having this age.
Y	This mineral is using an age reported as an element mineralization period.
O	This mineral is using an age calculated from all data at the locality.
R	The age displayed for this mineral originates from a different, non-child locality.
P	The age displayed for this mineral is the range of ages for this mineral at all of this locality's children.
	This mineral's age has not yet been recorded.

Baryte	Calcite	Clay	Feldspar	Fluorite	Garnet	Mica	None	Pyrite	Quartz
Rutile	Spinel	Titanite

Andradite ()*	Ankerite ()*	Baryte ()*	Calcite ()*	Fluorite ()*
Magnetite ()*	Microcline ()*	Phlogopite ()*	Pyrite ()*	Quartz ()*
Rutile ()*	Siderite ()*	Spinel ()*	Titanite ()*

This Mineral list contains entries from this locality, including sub-localities. Minerals in bold are reported by mindat.org as occurring directly at this locality, and do not occur at any children (sublocalities) of this locality.

Elements at this locality, including sub-localities: Al Ba C Ca F Fe H K Mg O S Si Ti

Elements from minerals reported directly at this locality: Al Ba C Ca F Fe H K Mg O S Si Ti

Structural Groups for minerals in this locality:
Baryte Calcite Clay Feldspar Fluorite Garnet Mica None Pyrite Quartz
Rutile Spinel Titanite

14 IMA Minerals at location:

Mineral name	Structural Groups	IMA Formula	Max Age (Ma)	Min Age (Ma)	# of localities containing mineral
Andradite ()*	Garnet	Ca₃Fe³⁺₂(SiO₄)₃	145	100	1534
Ankerite ()*	None	Ca(Fe²⁺,Mg)(CO₃)₂	145	100	3092
Baryte ()*	Baryte	Ba(SO₄)	145	100	11547
Calcite ()*	Calcite	Ca(CO₃)	145	100	27770
Fluorite ()*	Fluorite	CaF₂	145	100	9617
Magnetite ()*	Spinel	Fe²⁺Fe³⁺₂O₄	145	100	14899
Microcline ()*	Feldspar	K(AlSi₃O₈)	145	100	4924
Phlogopite ()*	Mica Clay	KMg₃(AlSi₃O₁₀)(OH)₂	145	100	2273
Pyrite ()*	Pyrite	FeS₂	145	100	39462
Quartz ()*	Quartz	SiO₂	145	100	61156
Rutile ()*	Rutile	TiO₂	145	100	5614
Siderite ()*	Calcite	Fe(CO₃)	145	100	6417
Spinel ()*	Spinel	MgAl₂O₄	145	100	1934
Titanite ()*	Titanite	CaTi(SiO₄)O	143	129	4899

Locality Notes from all Ages at Locality:

Age ID	Locality Notes
Jen_0000746	MAGMATIC STYLE: Multiple plug comprising two arcuate and a central intrusion of carbonatite, and rare sheets amongst surrounding fenites. ASSOCIATED SILICATE ROCKS: Nepheline syenite and ijolite sheets; nephelinite, phonolite, trachyte, alnöite and camptonite dykes. Potassic and sodic fenites.
Jen_0000747	MAGMATIC STYLE: Multiple plug comprising two arcuate and a central intrusion of carbonatite, and rare sheets amongst surrounding fenites. ASSOCIATED SILICATE ROCKS: Nepheline syenite and ijolite sheets; nephelinite, phonolite, trachyte, alnöite and camptonite dykes. Potassic and sodic fenites.
Jen_0000748	MAGMATIC STYLE: Multiple plug comprising two arcuate and a central intrusion of carbonatite, and rare sheets amongst surrounding fenites. ASSOCIATED SILICATE ROCKS: Nepheline syenite and ijolite sheets; nephelinite, phonolite, trachyte, alnöite and camptonite dykes. Potassic and sodic fenites.

4 Ages assigned to this locality:

Excel ID	Max Age (Ma)	Min Age (Ma)	Age as listed in reference	Dating Method	Sample Source	Dated Mineral	MinDat Locality ID	Dated Locality (Max Age)	Location as listed in reference	Reference	Reference DOI	Reference ID
Jen_0000746	130.9	130.9	130.9	K-Ar	biotite		26432	Nchisi Island (Chilwa Island; Shirwa Island), Zomba, Southern Region, Malawi	Chilwa Island	Woolley and Kjarsgaard (2008)	10.4095/225115	GSCOF5796
Jen_0000747	143	129	136±7	K-Ar	titanite	Titanite	26432	Nchisi Island (Chilwa Island; Shirwa Island), Zomba, Southern Region, Malawi	Chilwa Island	Woolley and Kjarsgaard (2008)	10.4095/225115	GSCOF5796
Jen_0000748	133.5	118.1	125.8±7.7	K-Ar	zircon	Zircon	26432	Nchisi Island (Chilwa Island; Shirwa Island), Zomba, Southern Region, Malawi	Chilwa Island	Woolley and Kjarsgaard (2008)	10.4095/225115	GSCOF5796
ree-00424	145	100	Early Cretaceous				26432	Nchisi Island (Chilwa Island; Shirwa Island), Zomba, Southern Region, Malawi	Chilwa Island	Orris and Grauch (2002)		USGSOFR02_189

Sample	Source Locality	Reference URL

All locality data graciously provided by mindat.org

All age data...